I'd suggest going with the tried and true delayed block announcements that deepbit and now btcguild also use - people already know this method and it's easy enough for the non mathematical mind to understand, so they'd probably trust it more than other solutions such as pay per last N shares.
Delaying announcements is NOT going to help anything.
As soon as 3-4 bigger pools run delayed (currently only 2 huge pools run delayed prop.) there will be measures against this. The only ones who loose are the regular miners again, as they get less transparency but still get hopped.
Also a code change like this might introduce bugs while only being a temporary measure. Please rather invest your time and ressources in implementing a safe payout method instead of trying to secure an algorithm that is broken by design.