So I get from the OP that little modifiers (like in Imperator) are bad and "flavour" is good. Since Victoria II didn't have a lot of "flavour", the OP doesn't seem to have liked that.
In my honest opinion, "flavour" as in TAG-specific mechanics ought to be avoided. Why? Because it makes certain events outside of the game instead of flowing from it. It makes countries themselves having a character instead of the people inside them. It fuels that fantasy that countries have essential qualities. And this idea did a lot of harm in the past, since it allows people to then claim that their country/culture is "stronger" than another one.
To me, it's more than a game design disagreement. It's a philosophical opposition, a visceral cry against racism and blatant misrepresentatino. So much so that I really "hate" flavour made in the form of mission trees and national ideas. It sends the wrong message to thousands of people who claim to like history. The excuse that this is a game doesn't hold water, if this medium promotes a caricatural version of history.
I get that to correctly represent certain events that happened near the beginning of the game, you need to place countries in an initial situation. However they trigger the start of the hundred years war, though, I don't feel like you need a specific mechanic to tell this story. Rather, you need a dynastic system sufficiently robust to entertain the possibility that England would claim France's throne since the Capet dynasty died out recently and there was an obvious dynastic link with the Plantagenet in England.
A lot of the enjoyment I can feel from a game comes down to how complex its main mechanics are. Societal values seem to me like a way to represent a lot of countries differences from the start. Laws and government reforms too. Ideally, any country should be able to have any setting with time and patience, meaning there shouldn't be mechanics restricted to TAGs, but some should be a lot closer to access them than others based on their internal setup at the start of the game.
For those things that aren't represented from the start of the game, like the Hussites or the reformation, general mechanics with the possibility for regional divergence (such as, if an heresy starts in Bohemia, it may be called "hussite") sounds like a nice cherry on top of an already robust simulation, but I want the game to go no further. Same for historical events. They may be called like their historical counterpart, but you need to keep in reserve an equal generic brand : if you have the English war of the roses, keep a similar civil war for other countries. If you have militarization for an eventual Prussia, let other countries have access to it.