In My Experience:
The hosting part isnt hard but there is a ton of file managment. Alot of script writing. Try to find someone who thinks things like that are fun.
Windows servers running only tcpip games would not be able to run very many. I suppose you could start a new game every month and hope that the fact it will run more than a month will keep it from being the same people joining every game.
Interfacing to web pages for game stats I think is an important feature that is rare and shouldnt be overlooked. Interfacing a web page for upload/download of turns is a security concern but there are plenty of tested scripts for that.
Setting it up for PbEM games would be more efficient altho abit more to iron out.
Linux would me more efficient. You could run more tcpip games on less server.
Linux running in text mode would be the most efficient. More games could be run and its much eiaser to interface to webpages. But its not easy to dive into linux text-mode. A background in other text modes, even DOS, is a big help.
I will happily provide all my scripts. Or even provide an account to someone you choose and let them poke around.
Here is a game-start page I messed with abit (it doesnt start a game).
http://www.dom3minions.com/lab/MakeGame.htm
But I decided that my server would not support everyone starting a game whenever they were in the mood.
Gandalf Parker