Political support

Mh... I like the idea although I find it likely to introduce too much micromanagement to the game. It would be a nice addition as a DLS though.

I understand you warranted worry.

The vision I have of this would have players notice that they are lacking support for "Progress" ideology while wishing to pass pro-progress reforms, so they go to the "political" screen to check what is going on over there and notice that there is a lot of opposition coming from rural folks and science districts. Decides to attach a couple territories and appoint more researchers to have those numbers change for the next turn. Which happens to synergize with the "progress" reform the player is about to pass. Or maybe they start fiddling because a city is entering revolt and they are looking for ways to calm them down; maybe repelling some odd civic may calm the rioters?

But it can easily end up being disconnected, vague and confused bonuses that ends up making the player feel like the entire mechanic is just random and frustrating.

I think it could be safe to try making a "superficial" version (minor bonus/penalty allowing players to basically ignore the mechanic and only see it as flavour or almost, like I personally viewed the Loyalty mechanic in civ6 that seems useless given the governors' impact on it) but making any deeper would indeed end up as a DLC given the required thinking & balancing from the dev (and players).

Point is giving more tools, more "events", more flavour... but to not simply make it tedious nor a hassle to play as it ultimately needs to be fun.

PS: Just realized that "Osmosis" and the Congress both have influence on Civics reform and would cause serious issues for players whose population's will is not aligned with the international community (or the contrary; a player seemingly "immune" to the Congress as their people are fanatically loyal). I'll admit I haven't played enough of the late eras with the expansion to be able to tell if this would be a problem or actually helpful.

I quite like the idea, and it closely resembles the system employed in Endless Space 2, which in theory would make it easier to adapt and implement in Humankind.