Have you considered just giving your players open bonus feats at certain levels? I tried something similar to your solution in my game, but found that who needed what and when could vary considerably from build to build. It turned out to be much easier to just give everyone a few bonus feats of their choice early on in order to allow them to get those "must have" feats out of the way. With that taken care of, my players were free to pursue less optimal options that seemed more interesting to them. It was easy to do, and I didn't see any real power creep because there is a diminishing return when it comes to feats. You only have so many worthwhile choices for a PC's primary focus, and the extra choices just become little bonuses that add flavor or allow your character to do a secondary schtick well enough for it to be a viable option.