I can agree to both of those. Working on the curse, modeled after the Vargouille:
Death Sheep Curse (Su): Any creature damaged by a death sheep's bite attack must succeed on a DC X Fortitude save or be cursed to transform into a ravening lunatic. On the each day following the curse, the victim suffers two points of Wisdom drain and develops an urge to attack all other living creatures, which becomes stronger as the Wisdom loss becomes stronger. Once the victim's Wisdom drops to 0, it is immediately healed of its Wisdom drain but becomes permanently insane and goes berserk, attacking anything it sees, using only its teeth. At this point, the victim also gains a bite attack that deals 1d4 hp of damage (plus Strength modifier) as a natural attack. The only way to halt the transformation before it is complete is by casting remove curse, cure disease, and neutralize poison on the victim; once the transformation is complete, the victim can only be restored by the wish or miracle spells. The save DC is Constitution-based.
I could see Cha-based, but we'd have to bump the Charisma, then.