A rehaul and expansion of diplomacy. You should be able to bribe other nations into wars against their rivals in limited situations, but even if I give Brandenburg 1000 gold it can't overcome or have any impact on the diplomatic score at the moment in any case.
Stuff like that, look at Civ or some better political game and boost the choices in EU4. I know they don't do it because the AI is pretty crap, so maybe work on that.
I would totally buy a better AI expansion, but I don't want to fund Skynet, so not too good.