I do not mind difficulty that much - yes, Ascension breaks game balance, but I've yet to see a mod that presents a tactical challenge and doesn't. It's either too easy or too difficult.
I'm not really sure what you're looking for here. Of course any mod which increases the difficulty of a specific part of the game is going to disrupt the overall balance, because the game is already balanced to a degree; it's no secret that installing Improved Ilyich makes the rest of the game look stupid. The only solution to not disrupting balance is to consistently raise the difficulty of the entire game, in which case DEF JAM is pretty much all you're looking at.