Well, there'd be a limit on greater mutations of course, not to mention then you'd be going for a longer time without upgrades while all your cool new chaos brethren are showing off their cool new minor gifts from the dark gods.

I'm still just not seeing a reason to go for the minor, man. "Look at this cool tentacle I got!"
Meanwhile:

Like I said, there'd be a limit on major mutations, and maybe they could add something like a risk of becoming a spawn (If only temporarily) from taking too many large mutations/too many mutations in general.

I'm more impressed by the impractical wings.

on that note, I hope there will be mutations that will affect gameplay, such as a claw hand or tentacle as well as aesthetic ones besides just a bloated belly for nurlgites. Examples could be a demonic mouth and tongue (think Venom from spiderman) or half your face missing, exposing the skull and musculature beneath.