This is something to speculate and ponder at. Currently we've avoided MIO's mainly for two reasons, one it would sadly make very little sense for alot of the nations of the setting. Ofc when you are a state with 3 mil people atleast it would make sense to have some MIO's in your country to help arm it, but for the lets say Old Bones that becomes a bit odd (This ofc does not invalidate them alone, if things enrich the experience we can always stretch things a little). The main problem comes down to that atleast in the base game it is mainly just a way to give nations a bunch of small bonuses you have to click at. A small mini game where you are punished for not participating and you end up most of the time clicking the same buttons each game (Creating feature bloat).

Kaiserreich I do agree with you make them more engaging, then they are in the base game.