I believe grenadiers are on the short list for getting the axe, along with scientists.
They’re being replaced with robots, eventually, I believe, and there was at least discussion over bio-operators as well. I don’t know if they want zombies using cbms. I like where your head’s at though, looking for the workaround.
I don’t see any reason there can’t be fire enemies, I just don’t think they’d want it to be a ‘zombie’. Could you make a robot that uses a flamethrower? 100%, I bet that would be met with a bunch of thumbs up. Could you make small skitter bots that track the player and then blow up when they get close? Sure.
It’s the zambie part that raises the red flags for me. All just my opinion, of course.