Conclaves do Jack
all percentage bonus buildings are worthless
First off ... under the current mechanics, Enclaves are too big and too worthless. Increasing a conclave's percentage to 100% science would make it a worthwhile build over a school or library.
Same with all percentage buildings, too big and too little gain. I would advise for conclaves to be 25% science and only 1 tile large. Slums are also "not good enough" yet.
Slums right now are a fourth the cost (in gold) yet are equal cost in Housing/Squares ratio. This would be FINE if the food cost was significantly lower. AKA, Slums should cost only 10 food, 4 squares, 50 gold, and -1 (or -2) prestige. That would even things out a little more (and make it a worthwhile build for the NON-renewable resource of city space).
I mean ... all of these problems could potentially be alleviated by increasing the number of squares available for a city.
I propose a "Civil Engineering Office". This would be a 1 tile building, costing 100 gold and 20 wood, available at (probably) refined administration OR refined civics OR civics. Building this building increases available "space" of a city by 4. This gains you a net of 3 extra squares for each Civil Engineering Office built. (building the office takes 5 turns.
In addition, I think that the building that reduces building times (warehouse) should either reduce times by 20%, or refined administration should allow for an Expanded Warehouse that reduces build times by 20% (1 tile building). Of course, only 1 expanded warehouse can be built per city. Those 10% additions can be built, but only a max of three regular 10% warehouses. So, you can use 4 tiles of warehouses (one expanded warehouse and three small warehouses) to reduce building times by 50%. This seems like a fair gain compared to other high-end 4-tile buildings.
and Finally, I know they are planning on this last feature, however I wasn't convinced (I'll check a few more times) that it was fully implemented. Any city that produces a Numeric value should have that value multiplied by city-size. (unless its a material?)
So a Market(4 gold) in a size 3 city should produce 12 gold per turn. A Town Hall(2 prestige) should produce 6 prestige per turn.
Also ... now that I have been playing with the system some ... and considering that output should be multiplied by City Size ... I no longer see a need for buildings to be restricted to city size. I am currently of the opinion that any size of city should be able to build any building. The two main factors that influenced this change of heart was (unique research/long research) and (restricted city size)
Meaning, that due to long research times, an investment in research could lead to some odd results that are asymmetric to your empire in terms of population/ect. Also, the limit of buildings due to city size is a good limiter of this function. What I mean, is that investment in technology is ENOUGH to allow the building of said structure immediately.
A latter building that serves the same function as the prevoius building should either give more profit, or cost less. Houses give more profit than huts ... however monastaries should either cost less, or give more bonus than a Conclave. And of course reduce the size (or vastly increase the profit, OR increase amount of squares you can build upon).
Meaning ... that if I want a Science city, I can build 3 schools (24 science) or build 2 schools and 1 conclave (20 science). Conclaves only become equal to schools or Libraries (schools and libraries are equal in size/output ratio) once you have 4 schools or more. This is always true, even if School output is determined by city size, it will always be better to build a school until you have 4 or more schools ... and the odds of having 4 schools is next to none unless you have a city that is extremely specialized.