P-G: We have to hope the seed will sprout, and keep our fingers crossed! You've got the creative spirit.

Placing cannons on the grand board would definitely alter the complexion of the game. I would be more amenable to the idea of a "pure" cannon; that is, one that may fire a given distance (say, for example, 4, 5 or 6 spaces), not with the need for an intervening obstacle. Either way, I suppose their range would have to be limited somewhat, otherwise you just get into a free-for-all. In other words, you must move them out into risky territory in order to make them threatening. Alas, I remain a bit skeptical that they could prove to be too powerful, and spoil the idea, or otherwise pose some flexibility problem with a grand variant set........ An extra Card is a bold proposition. It's a dangerous piece, and having a pair of them per side would make matters much more challenging.

I was trying to imagine how your idea would work on a 12 (vertical) by 10 (horizontal) board. It would be neat if this site (or some other) offered something like an "idea editor", a system in which games could be played strictly off the record by setting up your own board size and piece array of choice, just to see what might happen by experimentation. In this way, a handful or so games could be tried, and then you might modify it; something you assumed would be useful might not turn out to be, but something else you had not thought of at all could come to mind. I don't know how difficult this would be to arrange, but there is already a game editor for screen chess and others, so it doesn't seem too problematic.