I'm thinking on paying a blackjack double instead of 3-2 ( so I don't have to fool with the $25 chips.) Not sure on this one yet
I deal a blackjack tournament at the casino where I work, and this is what we do. If you pay someone $150 on their $100 blackjack, and then they bet $125 and get another blackjack, you're stuck.
As for players deviating from basic strategy, that's in some ways what's great about a blackjack tournament. Based on the size of your bet vs. the other players' bets, you might WANT to screw up the hand. Also, if you have a big bet riding, you have to be able to compensate for other players' plays. All of this psychology is why I absolutely love blackjack tournaments.