Terje - I will take a look at your work, sounds cool. It sounds like you know a lot about the swank protocol, so you'll definitely be good for swank-gambit. I'll check out your RPC layer to see what you're doing!
I'm not a SLIME user but I just happened upon this, it sounds relevant.
http://common-lisp.net/project/slime/doc/html/Global-IO-Redirection.html#Global-IO-Redirection