If you'd prefer to use Scheme over Common Lisp and would like to get your hands dirty, consider hacking on guile-wm. I try it out from time to time and make small patches to improve it. You can modify guile-wm at runtime by connecting to the REPL server using telnet or the geiser Emacs extension. I recall StumpWM not having something as convenient. I wish guile-wm was under more active development, so maybe a few mor…
It's been years since I've used StumpWM, but I believe you can accomplish a similar setup using SLIME ( http://www.emacswiki.org/emacs/StumpWM ).
I liked StumpWM when I used it, but as a Schemer, I'm inclined to use/hack guile-wm.