Yeah, how about the whole, say, security going full thug and running around mugging and torturing people (HoS will pretty much become a gang leader)? Engineering making breaches everywhere, or filling the entire station with N2O? Scientists going apeshit, hacking AI, building mechs to guzzle the cash from all other crew (not to mention they can both make extremely powerful bombs, and the means to repair the breaches).
The point is: why do you think heads will keep their departments in line instead of going for a powergrab?