Isn't that already how EU 4? You accumulate a lot of Monarch Power (effort) and spend it either on tech to get a bunch of goodies or idea sets which let you customize your nation? The only difference I can see is that inventions are passive and have a chance to happen while ideas require investment before they pay off.
So i need to explain myself better.
In victoria 2 and stellaris you research something and it takes time for it to complete.
In eu4 you just spend monarch points for instant research.
On the notion of passive bonuses.
In this sense i mean less immediate bonuses, eu4 gives army morale, trade efficiency etc.
Immediate bonuses.
I rather have i guess, +5% pop growth speed, -5% building time, -10% advisor cost.
Etc. Small bonuses that are more passive, not instant boosts. They are useful, but not massive.
Besides that you need things like inventions and upgrades, new army types, new boats, new buildings etc.
I think technology has solid base right now, but Imo institutions work strangely for me. Maybe tying them with pops instead of dev will resolve the problem, but looking at India and China I doubt it. Requirements to get are set mindfully in terms 'what should I do to get colonialism', but outcome is mostly ahistorical, because Europe was "overtaking" rest of the world with some acceleration(slowly at the beggining of EU4 and pretty hard at the end). Yet in the game it's other way around, we have some sort of westernization in XVIII century, because everything after Printing Press is pretty easy to get everywhere in the world. I don't even mention dev pushes, with pops it should be way harder to push institutions.
Also establishing colonies with pops will make more sense and prevent colonization rush with Australia fully colonized in 1600s.
I would consider splitting also in : rural, townsmen, clergy, nobility. And tie it nicely with estates.(with DLCs special pops like cossacks could be added)
The issue with technology is that a tech 20 player has such power creep against a tech 5 player in economy and trade. Technology in eu4 sorta represents dynamic pop growth.
Military it makes sense with efficiency, but with manpower and force limit growth, and with economically and trade, less so.
Now with regards to pop types.
Inherently its not needed. Eu4 is not viccy2, estates are based on landownership, not population. Hence peasants and serfs aren't included.
Now think of it another way, why include it when there are more abstract systems that can do an easier job of it.
The estate thing nowadays is abstract, the estates no longer own a province.
And I like it a lot more.