I've been mulling over decisions on how an X-23 film could work while debating on what rights are present within Fox's wheelhouse for it to work with the best audience retention as well as the best way to help establish and grow into other franchises.
Previously I've talked about how the "Old Ghosts" story could be adapted and should be adapted for a first X-Force feature, but considering that path would need an established X-23, the origin tale side of her needs to be explored too.
Currently, this is where I'm leaning.
If they do the origin tale of X-23 which is a combination of Target X and Innocence Lost, we get the first half of the movie to be a tale of Laura's mother, her growth, and then sacrifice to save her daughter. Of which I am leaning on Lucy Hale as the best actress choice for Laura Kinney herself. The story needs minimal changes other than establishing Kimura into the earlier timeline as she was retconned in using Target X. These changes to Kimura's story also present a unique opportunity to fix a few story points besides better expanding on the genetic connection between Laura and her mother that many gloss over and ignore. (The comics are clear, she is related to Logan by his mutant gene, but everything else came from the mother's side.)
The changes to Kimura's character I would personally add, is because of Zander Rice's failures, he outsourced her power set creation to Nathaniel Essex aka Mr. Sinister. We've already seen in the miniseries that he was also a potential bidding client on X-23's assassin services himself, so this would not be a far stretch at all because that bidding aspect shows he was fully aware of the Facility and their actions anyway. The other aspect that I'd change for Kimura is to have her be a human trafficking kid survivor that Zander Rice "saved." This altering of her story after she was orphaned and her grandmother passed away creates a valid story point on his molding her into sharing all the anger and hatred he does. This creates a better push on why she wouldn't turn against the Facility and has a more driven vendetta against X-23 herself because of X-23's killing of the man that saved her and gave her this twisted purpose. Casting for this with those changes makes me want to lean towards Shay Mitchell more than the previous choices I've listed. She has been an advocate for the Somaly Mam Foundation for awhile now which is an organization combating human trafficking in Southeast Asia. These film changes give her a larger talking point and can also contribute to her cause by highlighting the nature of that industry if albeit briefly. Her cheery demeanor and acting range provides a tangible creepiness to the role of Kimura as well that could send chills down anyone's spine. This is the exact kind of emotional conveyance the character needs.
For other changes, because of rights issues, Captain America and Daredevil are off the table from the Target X side of the origin tale. That's not necessarily a bad thing though. Daredevil's lawyer role and human rights talking point as a conscience and lie detector can be replaced easily enough with Douglas "Cypher" Ramsey of the New Mutants. With S.H.I.E.L.D. also removed from the story for rights reasons, this could be used as an opportunity to establish the Mutant Response Division. A federal agency tasked with co-operative actions between humans and mutants that handle mutant affairs and crimes. This change establishes them into the modern X-Men film continuity, and presents an opportunity to have Agent Neena "Domino" Thurman to be used in Captain America's role. This presents the best direction that I can see, because it allows for Domino to be established as a character with her veteran agent history before turning to work with X-Force. Having experienced first hand the corruption within the ranks of the MRD and handling X-23's case which could be the final catalyst to her leaving the agency to handle these matters with X-Force outside the law and how she's aware of Wolverine himself.(Can you say perfect mid-credits scene?) That pretty much leaves the rest of the X-23 origin tale unchanged and also presents a more understandable reason for why X-23 could have been caught by her because of Domino's "luck manipulation" based power set.
So that sets the origin tale aside as locked for best direction to world build and begin establishing pieces for other parts of the franchise to draw upon. It presents us with an experienced bad ass takes-no-gruff female agent that can relate to X-23 and gives us the conscience that a not as-naive-as-his-age-would-suggest mutant affairs lawyer liason yields. Douglas Ramsay being the voice of reason to suggest that the MRD would want to simply use X-23 as others have voices that kernel of truth that could make Domino hesitate and change her mind as Matt Murdock's similar words did for Steve Rogers in the story.
For the follow up movies, this allows many directions. The NYX story could be covered as it is considered a period of grief for X-23 anyway as she has lost her family, and began slowly to lose her way not knowing what to do or what her mission is anymore. This builds to the Kiden story and could further handle those issues and dive into these topics like teen homelessness. That story would need minimal to no changes as there are no rights issues present within those confines and the changes made to the origin do not impact the story material needed.
From there, the events of an "Old Ghosts" X-Force story can take place. Of which the only thing absolutely needed is the ending teleport save that sets up "Not Forgotten." This could be accomplished with Deadpool being the teleporter which can highlight how his powers do not always work as intended, especially without Domino to guide the probability of full success. It also presents a story point of Domino recruiting X-23 herself for X-Force in a recruitment montage as discussed previously here. This story of anti-mutant terrorists that the MRD ignores using bio-warfare tactics to further instigate hate crimes against mutants also dabbles into prevalent world issues we've seen recently. It provides a symbolic talking point and commentary on the analogies that the X-Men stories are known for. The teleporting scene itself would essentially be X-23 bracing against a wall ready to run. She runs, Deadpool grabs her hand and swings her into the air as he attempts to teleport her to the location to stop the last mutant from being infected with the virus. Providing a scene with her teleporting into the warehouse, popping her claws mid-air, and striking down the last of the terrorists. Her being fueled by adrenaline of the moment makes her look past the pain of her internal organs being scrambled a bit from the teleport jump. Which causes her to faint after she stops the terrorists for her to be incapacitated for the MRD to capture as they burst in right after she saves the last victim. (So it'd be, braced against the wall, runs, Deadpool grabs her hand and swings her upwards into the air as he teleports her. She appears in the air at the warehouse where the terrorists are, pops her claws mid-air. Comes down on two with her claws, taking them to the ground with her crouching as she lands on them. Then she takes out a third with a her foot claw as she handsprings forward back onto her feet again, grabbing his gun as he falls, and lastly shooting the final one that's about to infect the victim. Then she faints from the stress of the teleport and her healing factor still trying to repair that damage done from it.) Similar to what's presented at the start of "Not Forgotten" but with a more action oriented powers associated spin that doesn't involve the time travel story line the comic run used.
With these changes in place, we come to the X-Force tale of "Not Forgotten" that continues on from the remnants and remaining heads of the Facility as well as Kimura herself. For this story, because of the rights issues, Agent Morales would need to be replaced. Because of the changes already present by using the MRD instead of S.H.I.E.L.D. it allows for a rookie MRD human female agent(which personally, I'd recommend Selena Gomez for this role) to be given Domino's case load from when she quit the agency.
With her youth being under fire, and her peers being less than pleasant to her because of her gender and more, it presents a story point of ageism and sexism within the agency besides all the other aspects talked about. This yields a chance to have her be a top trained and top of her class agent, but because of her youth and what they believe is her being naive in trying to help people, she isn't taken seriously and is given the cases no one else wants. One of which being X-23's case file because it was red flagged as high risk. Something that would be common with Domino's case files because of her luck manipulation power set. This allows for a better story point of the bond she and Laura make in the film as this rookie agent deems what the MRD is doing and their wanting to hand "the X-23 weapon" back over to the Facility as being wrong. It also shows her turnover to do the right thing in spite of what the higher ranking officials tell her to do more believable than a veteran-hardened-by-experience agent that might look the other way because of orders(an element that plays up to why Domino left the agency). It allows better audience retention as the ageism displayed gives a point that's easy for a younger crowd or anyone that's experienced that kind of dismissive attitude to relate to.
This comes back around full circle with the end of "Not Forgotten" as the rookie agent by the very nature of being a rookie would be someone Domino isn't familiar with and does not trust because of this. Which in turn provides X-23 an opportunity to stand up for this rookie agent, and though the rookie is human, she could become a silent partner to X-Force's actions by working within the agency to kick cases and information their way for future film franchise usage that further shows she also sees the problems with the MRD but believes that good can still be done from where she's at. The rookie genuinely believes in the cause that the MRD was founded on which is why she worked so hard to be top-trained and the head of her class academically. With the building itself having been decimated in the aftermath of "Not Forgotten," this rookie agent would be the lone survivor from the MRD agents there and the story she tells back at home office the only evidence they have as to what happened. Kimura swears a vendetta against X-23 at the end of the story, but works with the Facility, not the MRD. Whatever she tells would be only on file at the Facility and not with the MRD because the MRD agents on the payroll would have been mostly dispatched when that Facility location was decimated by the fire and explosions. Any that might be aware would only out themselves as cops on the take at the MRD. Pretty much the same as the events in the comic.
This of course also provides a later on potential for Fox to dabble into having X-23 become the new Wolverine when Hugh Jackman is ready to retire from the role, and fully establishes her character history along the way as a character audiences are now familiar with.
All in all, this where I'm personally leaning that could provide the best results for the franchise, as well as fully establish some of the key points of X-23's story for the cinematic world. While it does change a few elements, it leaves the soul of the property intact as well as provides enough comic nods that it should keep everyone happy with the conveyances and generate the best revenue returns as a whole as well as open story directions for other parts of the X-Men rights franchises.
With the actress choices leaning on several outspoken people on many of the topics that the stories entail, this also provides ample opportunity to highlight the causes they are passionate about and provides a vocal opportunity to bring these issues into the light to help raise awareness and funds per each's endeavors. Add in the initial all women behind the scenes approach proposed for the origin tale and you have a multi-faceted approach that not only could be fun to watch and experience on the big screen, it could make an impact and help further provide change that's much needed in the world.