As explained in the True Reincarnate thread, I don't like the idea at all, mainly because it conflates respecialization with progression; you can't change old choices without also paying the price to get new features. If the devs want to allow a character to spend a feat to get some minor ability of another class, fine... but it doesn't have to be tied into a reroll. (Which among other problems, is unsupported by the D&D rulebooks).
However, work on Past Life feats has already been done, and I doubt they'll be going away. So here's a suggestion to broaden their availability:
Allow either Past Life: X or level 1 X to qualify a character for the corresponding new feat.
For example, a Wizard could take Initiate of the Faith if he had either previously been a Cleric and used True Reincarnation, or if he currently had at least 1 level of Cleric. It seems clear that this wouldn't hurt anything, and would make various kinds of suboptimal multiclassing a little more helpful.
Additional suggestions in support of the above:
The monk feat- In addition, you have Improved Unarmed Strike, and the Evasive Trance will bump you to Imp Evasion if you already have Evasion.
The barb feat- If you already have a Rage ability, you instead gain +1 use.
The cleric, wizard, and fvs feats- You also gain +2 on UMD checks to activate spells of that class.
The paladin feat- Instead of lionheart, you gain an immediate reroll on fear saves, and have 2 uses of Smite Evil, which regenerate after 90 seconds. If you already had Smite Evil, you instead gain +2 uses.