Look, people are always going to be looking for and finding ways to bend any rules you set. If they don't want to follow them, they won't.
I think that the server owner should be able to decide how tight they want their restrictions to be, so that the people who want to be "artistic" (in the loosest sense of the term :P) can have their own servers, and the people who want good gameplay can play on servers with tighter restrictions. Yes, people will be able to make maps to fit an individual servers restrictions, but the server owner will be able to ban that map or adjust the requisites for that server.
Another good solution, possibly used in conjunction with the previous idea, would be an upload wl/bl, which would control who can upload a map to a server.
I think that the server owner should be able to decide how tight they want their restrictions to be, so that the people who want to be "artistic" (in the loosest sense of the term :P) can have their own servers, and the people who want good gameplay can play on servers with tighter restrictions. Yes, people will be able to make maps to fit an individual servers restrictions, but the server owner will be able to ban that map or adjust the requisites for that server.
Another good solution, possibly used in conjunction with the previous idea, would be an upload wl/bl, which would control who can upload a map to a server.