There was a mod where you could start off as a super mutant in New Vegas. Like a racial choice.
It was...Interesting. You were way bigger than everyone else, so often times you got stuck in doorways, or had your head up in the ceiling. You also had special super mutant versions of clothes and armour because good luck fitting a pre-war business suit on your giant frame.
It was a okay mod but I think the issue of the extra height would cause issues from the get go with making it official content. Also I think any professional developer would want to give something unique to super mutant movement to make it feel distinct from normal gameplay. So ontop of being too tall for doorways you also move with a lot more weight and strength. And thats just looking at it from a mechanical point of view, not the lore/roleplaying stuff that logically you should be getting shot at constantly which then feeds back into gameplay not being fun because you can't talk with anyone.
Another mod, maybe? Depending on how the power armour feels in gameplay you could make the heavy and slow movement of super mutants using those resources. Still would have to solve the height problem, which would require some sort of way to duck under things in a smooth way which hasnt really been achievable for mods. The story stuff of everyone reacting to you is impossible to make fun, the New Vegas mod made very little attempts at that, even with the Mojave being one of the more tolerant places for those guys. Would be nice to try it, though.