I'm certain the idea will be a no go.... But, nothing comes if you do not ask... How about a game route where you play as a pro-infector. No game overs from parasite bosses/minions, instead you fill the role of a carrier attempting to spread "your babies" the parasites.
The primary enemies could be other folks who oppose the infection, game play wise - it would function about the same combat wise with diffrant animations/portrates. And, story wise you could put the player in positions where they can gain their team-mates trust, infect them at night, and corrupt them (much like what happens to the main character atm).
If I have covered something that exisits already that I have yet to reach, or if you already have plans to impliment, just let me know and I'll remove the comment (and be excited to reach that part). *Corruption desires intesifies*