Alter-alternatively, the heritages in question could say "if you already have darkvision, you get an extra 1st-level ancestry feat instead." We know that upgrading low-light to darkvision is supposed to be balanced vs 1st-level ancestry feats because there are 1st-level ancestry feats that...
The closest rule that I could find addressing something non-witch familiar death is the Special entry of the Pet feat (from which familiars are based): "You can gain a new pet by retraining this feat, releasing any previous pet you have." Insofar as I can tell, it's either resurrection...
I have concerns about the flood of feats - awe and wonder at their ability to create vastly more diverse characters than the previous addition, but also a feeling like I need to be an expert on all of them otherwise ill probably let players do stuff that should require a feat。。。 i ...