There's already a 50% chance to mutate, but mutations are based on what content you bad-ended to. It won't be something you can choose, although you can use the 'Preferences' menu to turn off all the mutations you don't want to encounter and next update you'll be able to banish unwanted mutations as well.
'Worshippers of the Gain' and 'Asterism: Lawman' are done. I'll still be pushing bug-fixes for 'em though (And actually, a few bug-fixes are pending)! :)