your sheme will lead to orphan block at best ; )
but pool are NOT safe from dishonest miners.
Interesting, care to elaborate?
I've heard of pool hopping, where miners jump into a pool that has just solved a block in the hope of being included in the payout (I gather the PPLNS scheme excludes the current round just so as to avoid this), but what other nefarious deeds do pools need to watch out for?