If you’re looking for game ideas that are outside of the run-of-the-mill combat bonuses, I have some suggestions.
Proposal 1: Cloning
Here’s an idea for a SS that would be super cool for a hero but would probably be a pain to implement. Clone another hero’s SS. The Clone would copy the SS of another hero on the board, either ally or enemy. No other attributes or stats would be copied, just the SS effect.
If your enemy has someone especially rare or useful, you could use their SS against them. It would be delicious to turn a Guinevere or Gravemaker tank against their own team.
On a defense team, the clone would obviously have to randomly choose a target to copy in addition to any targets the original SS requires. And, something would have to be done so that a Clone can’t copy another Clone and cause a recursive loop.
Proposal 2: Make a diamond on the board.
So far I don’t think there’s been any hero that manipulates the board the way a Tornado does for example. I think it would be cool to have heroes that can manipulate the board. The simplest (to the non-coder me anyway) and most useful effect would be to change any gem on the board to a diamond of the same color and detonate it. This should not break anything in the board mechanics, but I can see it being somewhat abusive in anything faster than a slow charging SS. Although if you want to nerf such an ability, creating a skill that clears all gems of X color would also do something useful.
Making a diamond would be so cool to use against titans and in challenges.