Only making the expected return per next-share-contributed be totally independent of the pool history/round-lengths can strategic entry/exit be made profitless. One way to do this is to pay a fixed amount per share no matter what the relation to successful blocks.. but that requires the pool to have a reserve and insure the long dry spells.
MaxPPS is like this, but makes the "reserve" per-user so they can't cheat the pool by withholding blocks.
So it shows as earnings, but they're on hold indefinitely until you work some more? An amount held hostage to ensure loyalty?
Seems a lot like scrip you can only spend at the company store an abusive practice from the old company/mining towns of yore.
Strongly, strongly dislike this MaxPPS as described. Seems against the transparency/instantness that was the initial appeal of Eligius.
I can see how for a miner that commits to Eligius for 'now and forever' it eventually evens out to about the same as pure PPS (or PPLNS). But my guess is miners as a group have a very large discount rate given all the levels of uncertainty in the bitcoin economy, so a system that requires an indefinite commitment to get full returns will have a small audience.