OP, i have but one proverb for you, that perfectly summarizes my thoughts on your idea:
The whole is more than sum of its parts.
i'm not sure OP realizes all the consequences the Paradox financial model brings up. The biggest would be, that there would be no sequels or big expansion packs like gathering storm (or Civilization 6 for that matter), because these take months and years to complete, whereas the paradox dlc's do not.
Let me make a thought experiment. I will set a starting date after the release of CIV6 Rise&Fall.
We then decide to clone Firaxis into two completely equal studios and present each one with the following tasks, which they have to complete in 1 year time:
Firaxis A: This one has to create 1 expansion pack
Firaxis B: This one has to create 3 dlc's
With this scenario in mind, I would bet my head that Firaxis A would produce an overall better experience than Firaxis B.
"Why are you so sure?" - you ask
The big advantage is how features in civilization games that come bundled together can synchronize with each other in ways that aren't possible in paradox games because of compatibility concerns between various dlcs. If you take just one main feature away from GS like disasters or world congress, the expansion pack becomes 10x less enjoyable, not "a bit more empty".
If anything, paradox should learn a thing or two from Firaxis. Let new dlc's incorporate fatures from old dlc's if the features are good and could collaborate with the new features. Make a bit less dlc's and make each one of those more impactful.