Special followers like ||Narinder|| and ||Jalala|| are cool, but compared to my don't starve + polyamorous + ascetic followers they aren't that useful.
Being able to either swap two cultists breedable traits (so no transferring stuff like immortal), sacrifice an egg to give it's traits to another follower or permenantly sacrifice a follower to transfer their traits to another would be nice.
Personally, I like the idea of permanently killing a follower to give their traits to others as it means I can slowly clear out my resurrection list one by one.