That's no different than regular feats. Most feats are not universally considered by any class, with the odd exception. Past lives provide a passive option plus more choices in feat selection. Adding free feats on top of free feats just to get more of the active feats isn't necessary.
If any active past life feats need a buff to be worth a slot that would be a different story. A different suggestion to that scenario would also be the appropriate resolution; IE how to buff a weak past life feat.