This is a simple idea that adds an element of bluffing to the game. Taken directly from Songs of Anarchy game.
Before a battle both plays announce how many cannon tokens they both own. Then in secret they put into their hand the number they want to use. Both players reveal at the same time!
I like the idea, but the only slightly tricky thing is that the cannon could be coming from multiple holds. They'd need to put some kind of proxy in their hands instead, like cannon from the bank or other tokens if they ran out, or even cards.
It would also probably change the game a bit more in that people would have fewer cannons with this method. In the regular game, the defender gets to use cannon as conservatively as possible. With this variant, they'd probably waste a lot more.