Don't forget that my editor cannot add something that the game itself cannot use.
1) You can have several buildings, resources, technologies, governments, or units with the same name. In fact civIII does not use the name to identify objects, but a number.
I don't know why Firaxis forced the name to be unique.
However, it's not possible to have the same object with different names. How the game could find it? But what you can do is create a first generic building, and then make copies of it, and last rename it. So you will have Athena temple, Baal temple, etc.
But:
- You are still limited to a total of 256 buildings. If you have 20 civs and each one must have its own temple, you'll use 20 buildings.
- You cannot limit a building to a specific civilization directly (contrary to units). To achieve this, you can:
-- Use as requirement a technology that only this civ get, using non era tech. Ex: you give "Greek" as a non-era tech, give it to Greeks as bonus tech, and then make Athena worship requires this tech and polythesom
-- Use a resource: on a preplaced map, you can add a "Greek" resource near the Greek cities, and say the city need to have this in the city radius to build the Athena temple.
-- Use a government: limit the Athena temple to "Tyranny", a government that only the Greeks can get (via non-era tech)
2) You can edit, add or delete buildings or tech my my editor.
3) No. My personnal experience is that using Notepad is in fact much faster once you are used to it. However, my editor can tell if you there may be an error in your pediaicons.txt file.