I'm not opposed to the concept of "mana" in Paradox games. Victoria and HoI 2 handled them very well, I thought. Where EU4 went wrong is the straight abstraction of EVERYTHING into 3 simple mana pools.

Adding lots more types of mana is one way to handle that, and while not the most eloquent solutions, is probably the easiest way to go, from a modding stand point.

Personally, I'd much rather see a lot of these things be handled without mana. For example, culture conversion shouldn't cost a type of point. The way nationalism and primary nations affect it works well. I think the act of conversion should tie up an envoy or diplomat for the duration, and give a high amount of unrest for the duration, and then a minor amount of unrest for a while after, similar to the act of religious conversion.

The only things that should cost mana, in my opinion, are a few of the actions that already do. Stability, inflation, and government changes for administrative, negotiations and annexations for diplomatic, and the various military actions for armies and recruitment of leaders. Ideas, I think, should also maintain their costs. Buildings shouldn't have any cost associated with them, aside from their gold cost.

I don't know how tech should be handled, but I hate the way it is currently. Maybe something similar to HoI2, with a tech tree and you have to assign advisers to research them, with their skill and the date affecting research speed. That way, high skill advisers are still worth something, and Leonardo would have an actual profound impact on the progress of your nation. Treasurers and Masters of the Mint would get bonuses to economic techs, philosophers and natural scientists towards education, commandants and admirals to navy, governors and statesmen for diplomatic, etc etc.

So, yeah, ranted a little off topic. All of that is a pipe dream of what I wish EU4 actually was. Back on topic, I think more types would be a workable, albeit a bit heavy handed, solution for the mana problem.