would be kind of neat if slime could upgrade it’s slime trail to an acid trail like dark wryms get. That and being able to throw an eye ((At the expense of health)) to scout out your surroundings for a few moments.
As for eating bones, what about a rat or bug mutation that grants the ability to eat and gain some amount of nutrition from just about anything? Like the internal furnace CBM. Heck, you could even make a Wasp mutation like this that chews up organic matter (bones, wood, zombies, etc) and uses it to make paper walls.
Huge and Freakishly Huge mutants could quite possibly gain a brute smash for all their trouble. It would be admittedly satisfying to send zombie dogs crashing through walls.
Maybe give Cattle a trample attack? Damages an enemy, knocks them down and moves passed them. Great for forcing your way out of a crowd.