Having recently returned to Netrek, I've been looking for a timed game.  
However, it appears that RSA has, for some reason, been deprecated.  
Furthermore, it is not enforced, even on the clue servers.  Is there 
currently no scheme for verifying that a client is not giving its user 
an unfair advantage over the other players?

We must have some scheme for verifying that clients are valid.  Heck, 
most modern games spend a lot of their time ensuring an even playing 
field; look at CoD4/5 and Punkbuster, look at most MMOs (Lotro, WoW, 
etc) and their constant vigilance over client hacks.  This is as old as 
time, or at least, as old as gaming on the internet.  Make sure the 
other guy isn't cheating. 

How can you have a competitive game if you don't ensure a level playing