Make Mummies Immune to Rotting
Having no rotting on mummies is a relatively minor buff (effectively makes sources of mutation harmless to them) and removes the fidgety racial ability to deal with rot (which is necessary because of lack of potions). No potions, no rotting is simpler than no potions; still rotting, here's an ability to deal with it.
I'm beginning to feel like a Cat God! Felid streaks: {FeVM^Sif Muna, FeWn^Dithmenos, FeAr^Pakellas}, {FeEE^Ashenzari, FeEn^Gozag, FeNe^Sif Muna, FeAE^Vehumet...(ongoing)}