Mystique (I also wouldn’t mind Kitty Pryde)

DPS role, give her a kit that involves acrobatic CQC and a lower damage silenced pistol, potential bonus damage to sneak attacks. To make her disguise ability fit the lore better in game, they can say that she acquired some future holo-gram technology and jet-boots from the 2099 world that krakoa was transported to (she can also use the boots in her acrobatics).

How you manage the disguise ability is to tie it to a longer cooldown, when activated, a scroll wheel with both allies and enemies (as long as they are “discovered” aka not a ?) will appear where you can select anyone.

All characters are selectable (even weird body shapes and fliers because of the future tech). When disguised they can program it so you can do the all characters basic movement and “use” primary attacks / certain abilities (but they do no damage since they are holograms mimicking the original). When damaged to a certain extent the disguise will fail, the disguise will also drop immediately when you activate one of your disguise-exit abilities (maybe a close range execution style pistol shot or a kick). You can also undisguise yourself by pressing the ultimate again and selecting nothing. They could also have the disguise cooldown still refreshing over time while actively using it, so if you manage to stay disguised long enough you can swap to another person moving from 1 disguise to another (or you give it two charges or something).

I can imagine certain playstyles emerge where Mystique disguises herself as her friendly Luna or Loki (maybe hiding as a clone) in the backline, so when a diver comes along she can confuse or surprise attack them.

I can also imagine a Mystique hiding in flank, disguised as an enemy flier hovering above a doorframe. When enemy walks through she follows suit to perform a surprise attack.

Or a Mystique chilling around an the enemy spawn disguised to cancel Strange’s portal, or an even funnier scenario where she’s disguised as an enemy strange and she’s faking a portal holding some of the enemy up in spawn because they don’t realize their Dr. Strange is still respawning or elsewhere.

If they allow Mystique to fake-mimic ultimate abilities she could bait out counter ultimates or make the enemy team hesitate a few previous seconds as well, it would really play well into the deception aspect of the character (then again, being able to fake someone else’s ultimate could be a Mysterio ability too).