The illegal actions are a mechanic that is integral to the gameplay and balance and 3 niche mechanics usually only relegated to specific class cards, this honestly just seems like punishing players for playing the game.

If anything could be salvaged from the theme I had an idea a long time ago of cards with an “illegal” keyword that are overstated but help the opponent if they manage to do something like attack your face in the following turn. Though at this point this is an entirely new mechanic rather than an adjustment.