p2pool's sharechain already implement this mechanism. The only difference here is that each participant has a different view of what others have worked on because there isn't a reference of valid work to check (the sharechain). If someone is joining your distributed pool, they know nothing about the others and won't reward them with the expected amount so be rejected. The same problem will happen when a miner is temporarily down.

So you want miners in your distributed pool to have a way of sharing a known set of valid work (the very same for all participants unless you want to allow cheaters on board) to base their distribution on. The sharechain in p2pool does that, what's your solution?