Letting Nichelings live longer would also help role play! Or just people making amazing Ocs and what not out of the little Nichelings. For example you could decide oh this gal looks like she has her stuff together she isn't sickly.. let's let her have a long life, or if a nicheling saved someone but took tons of damage you could also decide to either have them die in the process or give them a longer lifespan than usual to kind of reward them? Also being able to choose the amount of food eten in a day would be fun because you could literally do a little feast or reward a Nicheling!
For most of these to happen though, I'm guessing if you were to edit life spawn in niche sandbox mode than it would have to effect everyone.. but if it didn't have to and was able to be edited that would be fabulous!