Perhaps make the fish thing Salt Ponds and/or Brine Wells? Preservation of Fish was a really big deal. I think you could justify a pretty big bonus. Maybe even an empire-wide one via a National Wonder type thing. (Or a per-city one based on a separate Fishmonger/market building then available in each city? Could you have them give bonus food only when you've got Fish? Could Fish be treated something like a Strategic resource and allow X buildings to be built per Fish? So many questions. Maybe I'll get the game.)
Anyhoo... Then give the extra farm yield effect to the Bakery? It think that's even easier to justify.
Don't have quite the capabilities of RifE or Wild Mana here yet.

Can't really have a different bonus available in different cities.
Not only can fish (and other food resources) be treated as strategic resources, that is EXACTLY what I'm doing. Most will have 2-3 resources on a plot, IIRC (set it up a few days ago

).
I may end up changing the fish bonus, in the process of implementing all the buildings now. Bakery is already in at 20% food stored and +1

, with Brewery as +3

-2
Leatherworker vs. Hunting Lodge:
I don't know what *you* get up to with leather goods, but I think a happy bonus would be more appropriate to the Hunting Lodge than the Leatherworker. The Lodge could give the populace access to a greater variety of foods, plus the fun of hunting for the rich and the fun of poaching for the poor. Outdoor fun for all, anyway. Picking mushrooms, say: There's a food treat for one and all. Plus it doesn't always have to be about gutting something.
Leatherworkers are instrumental in the production of lots of tools and protective garments - not only of the sort you seem to have in mind - and IMO could easily justify a production bonus.
Actually, I was thinking luxury goods. Leather couches, boots, jackets, etc. Could just as easily be applied for work clothing as well, though, as you said, but I like having the hunting lodge make forests more productive. It's an effect that is otherwise not very evident, and more interesting IMO than just a flat production bonus (which I would have to do with the leatherworker, can't tie it to forests

). So the happiness stays, as I
have to have some kind of effect to make it not worthless later on, with the armor only applying to earlier units.
Plantation-building name: With the inherent unhappiness you're evoking the slave-based "Plantation System" of the antebellum American south,yes? So how about "Plantation House" or "Plantation Mansion"?
I'd be a lot more enthused about the happiness hit - which seems like a good idea - if buildings could be destroyed. Or maybe just have Equal Rights destroy the Plantation building, or re-adjust the bonus/penalty? While it does make sense ER would cause more unhappiness with your Plantations, I think it makes even more sense that the Plantation is removed or the labor eased.
You could have a sharecropping Building that causes unhappiness and converts Farmed food to gold, or gives a gold bonus based on food. ("Company Store" is pretty good, but should have a relatively late tech-req? "Land Office"? "Owner's Manor"?)
Yes, that was Black_Imperator's idea with that one (He helped me come up with many of the effects on #erebus). Plantation House works for a name, will use it.
Hmm... Maybe instead of ER adding more unhappiness, I could have it
remove the unhappiness from the building, but also reduce the yields?
One thing to keep in mind: All of these buildings are maintenance free. Aside from the requirement of needing the resource, of course.
Edit: Also, the Sheep building is entirely changing; It will be much more awesome for some cities, less useful for others.
