Okay, it's been a topic forever here that Cryptic seems to be able to use any Star Trek character but is restricted from actor likenesses without paying individual actors.
This is why the canon characters we do have are grown up children, characters like Madred who already wore heavy makeup or people who have changed drastically in appearance like Harry Kim (now fat and sporting a moustache) or Donatra (I'll save you the spoiler).
I think it would be cool:
- To have Geordi revert to his mutated state from the episode "Identity Crisis but give him a uniform for modesty and have him go back to using his VISOR (a more iconic visual). It could actually make for an interesting backstory if he had to partially mutate himself back to that state to survive some kind of engineering malfunction aboard the Odyssey. It would help make him more visual and distinct in a game that goes beyond the standard TV show budget and should tend towards more dramatic visuals anyway. Plus, the makeup pattern is basically a more dramatic, glowing take on Tamarian makeup, which would be a cool addition.
- If a familiar character was brought back as a Kobali. This is a species that is made up of the dead, reanimated and genetically modified into a member of their species. Most retain no memories of their previous life but some do... and it would also be a way for someone from the DS9/TNG/VOY era to be relatively young and vital in the game. For example, maybe Bashir was killed in a medical survey to the nearest reaches of the Gamma Quadrant and brought back as a Kobali but his augmented DNA resulted in him retaining his personality and memories irreparably, forcing the Kobali to let him go.
- If Data stopped wearing his "skin" (perhaps in protest of the treatment of synthetic lifeforms, to remind people of his own synthetic status, to make a political statement) and simply took on a form roughly consistent with the glimpses we got of his metal frame underneath.
I wouldn't necessarily want to see these kinds of transformations become a schtick. But I wouldn't mind a handful to fast track a few familiar characters into the game as I'd rather have familiar characters turn up and the storylines be new than see us constantly experience things that we're told previous crews have experienced. New stories, old (if if mutated/changed) faces along for the ride with us.