I was under the impression that an ace of spades and a black jack was the first thing that got you 3:2.
Course, I didn't play any 21 in the olde timey days, so what do I know?
A 10-to-1 payoff would make it feel more like a modern day side bet than anything. So I guess I'd expect to see a complicated pay table even for just traditional blackjack. that would be kind of a drag.