Personally, I like where we are currently with districts, wonders outside cities. For me, the key things missing are just (1) I’d like Cities to sprawl outside their core tile more visually, (2) I think City Centres themselves could use a few more buildings (and a few existing ones, eg sewers, made more relevant, (3) a few more district buildings like the encampment’s barracks v stable where you have to choose between different building options, (4) Neighbourhoods to be more relevant, and (5) for the reasons stated in the OP, Farms to be more relevant generally (or at least as relevant as Mines).  Not including the government plaza, the only other examples are Encampment Barracks and Stable (already mentioned), Theatre Square Art Museum and Archeology Museum, IZ Power Stations and Neighbourhood Shopping Mall and Market. I guess Entertainment Complex and Waterpark is another example, but that’s at a district level. I think maybe Harbours and Commercial Hubs could use an alt building as their level 2 or 3 building. That would probably do me.