I'm not seeing the need to penalize one strategy over another here. The reasons to use National Culture levels in the first place are numerous. Believe it or not, favoring the smaller nation over the larger is actually one of them. If you think about it, the biggest reason a nation (usually a human player in this case) fails to go out for the ultimate landgrab and stays a bit smaller than its neighbors is due to the building of wonders. Not just a few but as many as you can amass. And when you do that, you end up with a small, compact, but powerful nation and the challenge at that point is defending your glittering cities cuz everyone wants them now and they assume you've been lax on your military. That small nation is far more culturally powerful than a much much much larger nation that has lots of cities but very little quality in any of them.
Sure size matters, but that factor is more and more as time goes on, which is going to be the same with research, gold, military, anything really. At least now with the leveling leaderheads in play, you have REASON to continue to care what your cultural output is in your core interior cities that have no more room to expand cultural boundaries, you have REASON to want to adjust the slider to culture (beyond just trying to adjust for some emergency happiness during war), and you have REASON to build culturally productive buildings when that's all they do. Finally... culture matters again and can stand on similar footing to Gold, Research, and Espionage in value.
I will respectfully have to disagree with this, again. *wink*
A small nation that concentrates more on Wonders and such will still be far, far, far, behind in any Cultural "War". The reasons are very simple really:
A) All of the small +1

B) Anyone expanding knows you need to get culture up in the new cities to gain territory and expand to be able to use the BFC as quickly as possible. Once there you can relax unless bordering on another nation but you will still have gotten to between 20 and 30

C) Wonders are great, but not for getting


D) Core Cities of course have more buildings and because of that also more




In finalization, to run a few numbers using my latest game as an example, which you all know I so delight in doing... *grin*:
In the beginning of Classical Age I have amassed 19 cities.
Of those eight are "Core" cities, some since long, some recently. Two cities are middling, leaving nine newly settled cities where a couple have reached pop 6 but most are between 2 and 4 in pop.
Capital has 145

The remaining seven Core Cities are between 90 and 118

The two middling cities have 73 resp 78

The nine settlements have between 18 and 54

If I had stayed with the eight Core cities only they might have been between 100 and 120


It takes at most one and a half Middling City to match a Core City, two to match the Capital.
It takes less than five settlements to match a Core City, my nine easily count as if I had 2 more Core.
So expanding without going expansionist and not Animal Culture Bomb



In a couple hundred turn time (not that long as it is on Eternity after all) I could be at 75% or more more than the 8 Core.
I remain on the opinion that the system currently favours expansionistic behaviour. Greatly.
Cheers