Can you make this pool running SMPPS mode , just like Eligius?
First, there is no way to store extra funds generated during lucky periods, because the pool can't keep any secrets from its users. (Using escrow payments might be possible, but has a lot of pitfalls - nodes could collude to steal pool's savings, nodes could go offline and money is lost forever.)
Some sort of hybrid scheme similar to...
A substantially different variant [of PPLNS] is to pay for every share at most once. If, when going backwards in the list of shares, we encounter some that were already paid, we skip them and move on to older shares.
...is definitely technically possible, but the size of the history of payments owed would have to be limited to prevent it from growing too large. Also, it would create a much greater reward from attacking the pool - instead of just nullifying the last 24 hours of other miners' work, an attacker with 51% of the mining power could create a separate sharechain stating that he's owed some enormous amount and override the history, forcing miners to pay any payouts during lucky periods to him.