I think the problem with +X/city is just that the policy is inherently hard to balance. Going from absolutely-overpowered to completely-worthless from a 1.0 to 0.5 drop means it's a very fine line.
Not sure that 0.5 is *comepletely* worthless, but there definitely needs to be some happiness policy here. Liberty is the tree about city-spam, and city-spam is restricted in part by happiness, so Liberty needs to have a policy that reduces the happiness problem of cityspam.
+0.5 happy per connected city and +1 hammer per connected city seems reasonable, particularly if you tweak the requirements such that it requires, say, both Representation and Republic.
Or maybe we should have:
Left side:
Collective rule, cities start size 2.
Citizenship, 2 free workers
Right side:
Meritocracy: +33% worker build rate
Representation: +2 culture per city
Republic: Requires Representation, Citizenship, +0.5 happy per connected city, +1 hammer per city.
If feels like Representation and Citizenship should be feeding into Republic, and that Republic should be the high end achievement here.
The power of the research-boosting policy in Patronage is why I moved the weakest policy (Aesthetics) as its new prerequisite... lessens the total effect of the 3-policy chain. I could nerf it slightly too.
I see your point.
I think its a bit hard to evaluate because I might see a huge boost in research from my city states and attribute it to this policy, but not really also consider how much science I could have got from eg buying libraries in my cities instead of CS alliances.
We could consider reducing it to 25% though, down from 1/3.
I really like the idea of a flat +X per-city boost deep in the Liberty tree, because it would actually combine well with a plan on my todo list to redesign Maritime city-states.
I think MCSs have already proved how problematic +x food per city is. Its an interesting idea, but I'd probably keep away from that, personally.
I guess though it could be a substitute from a happiness booster though, so it helps expansion but in a way that doesn't relax the happiness constraints.