I, like some others, enjoy experimenting with builds. Sometimes I do this on a main character with multiple past lives without enough forethought and wind up with a build that survives to about 12ish and then starts to flag off, HARD. Rather than just muster through and run upper end heroic quests at a lower difficulty until 20 and a TR I wind up making a new character with the latest greatest idea I have and lose all the progress I have on the other one for months on end until I finally get the ambition to finish it.
What I propose would be one more type of reincarnation heart, you could call it something along the lines of a tainted druidic heart of wood. It will allow you to completely reroll the current life (race, class, sex, everything) and retain all of your previous past life feats, but not gain a new one for the current life. You would start over from 1 (or 15 if you choose to go iconic) just like with a real TR. Yes, I know we have +20 hearts now, but sometimes you just want to swap everything around including the race, which a +20 heart will not let you do. This heart would be usable from any level.
I also propose that you make this cost tokens of the 12 just like a true reincarnation heart, but at perhaps half cost.
I have spoken with a few other people and aside from myself they would also be interested in something like this, as we all have characters that have been left abandoned because their build simply became un-fun as quests progressed into higher levels with third life+ experience requirements.