I think the main problem you're going to have, and even the original movie suffered from this a bit, is just to juggle the number of characters MK has. That said, I think if anything Infinity War has showed us you can juggle everything if you done the ground work before hand, which would mean having to build up to a movie about the MK tournament. Looking at it now, I wonder if an MK universe on film is actually a viable option, maybe not done with solo film, but maybe with clusters of characters for a few films before last movie about the tournament itself.
Now if it were me, Id mostly follow the rosters of each game with nothing more than small roles/cameos of characters in later games I mean, heres the way that the roster of the first three games built up:
MK1:
- Shang Tsung
- Goro
- Liu Kang
- Scorpion
- Subzero
- Johnny Cage
- Sonya
- Reptile
- Kano
- Raiden
MK2:
- Kitana
- Mileena
- Baraka
- Kung Lao
- Kintaro
- Shao Kahn
- Jax
Hidden boss characters: Smoke, Noob Saibot, and Jade
Mortal Kombat 3:
- Kabal
- Motaro
- Nightwolf
- Sektor
- Cyrax
- Ermac
- Rain
- Sindel
- Stryker
- Sheeva
So within a Trilogy of games 30 characters while also rotating some out whether its killing them off or some other plot reason.
For instance, you can introduce the roster of MK1 in the first movie with small appearances from Jax, Kung Lao II, Kitana, Mileena, Shao Kahn and Jade
- However you can kill off Shang Tsung, older Subzero and Goro while having Sonya and Kano get captured at the end of the film.
Youd have shown 16 characters in the movie but ended with 13 of them still alive while having 2 of that 13 set up for reduced roles in the sequel.
Now you can go with the roster additions of MK2 and youd then have a roster of 23 characters shown throughout the film with Kintaro and possibly Baraka killed off. Reducing the roster to 21 characters.
Then in MK3, you can introduce their roster additions while also downplaying the other characters in the way that MK3 vanilla did. Youd start off with about 31 characters shown throughout the film as a whole but have Kitana get locked up for killing Mileena, Johnny Cage get killed by Outworlds army, Raiden not able to fight alongside the heroes due to the merging of realms, Scorpion deciding to no longer fight for [insert reason here] along with Sheeva, Motaro, Shao Kahn and Shang Tsung all die in battle by the end of the film.
So that would be an active cast of 22 characters by the end of the film trilogy.
Since I highly doubt the 3D era has characters fans truly follow in the same way as they do the originals from the first 3 games