Also, I thought one of the major reasons to change reward system to PPLNS was to get rid of the infinitely growing shares database. I don't see any of these PPS variants helping in this respect. Then again if keeping the shares database also means we keep the current stats, then that would be a nice plus, at least until we have a new stats system in place, tested and tweaked to work with whatever reward system is in this pool's future.
Well, the problem with the share db is that it's HUGE and just gets bigger - it even includes the proof-of-work for every share. The data needed to support CPPSRB is relatively small, and can be sparse-deleted for every block we find (when I upgrade the server kernel to 3.0+).