I'd like to see the Casino Island Blackjack (from Pogo's free games) ruleset.
To make it reasonable:
Player blackjack beats dealer blackjack.
If no blackjacks, the next-highest ranking hand is a player 5-card charlie of any sort. (On the Casino Island BJ game, it pays 3:2 but we know that wouldn't happen.)
A caveat - if the dealer gets a 5-card charlie, they beat any remaining hands, including player 21s.
So the order of ranks would be player BJ > dealer BJ > player 5-card charlie > dealer 5-card charlie > rank all other hands normally.
You can't double after split, but can draw to split aces and re-split aces up to 4 hands.
Also from the same game, you should be able to earn the ability to have a bust negation - much as Casino On-Bar did in cheating in the dealer's favor by letting it second-deal to itself in certain situations. Basically, once you've earned this, the very next situation you would bust, the card that busted you is taken off of your hand and you are back at your previous total. If you double down and bust while having this bust negation, the doubling of your bet still remains (e.g. you double 12v6 and catch a 10, you're back at 12 and can play with that doubled bet. You cannot redouble.)