Re: Window manager switcher
seems you know the standard ways -- have a look at the wmanager
package (brandnew in potato):
$ apt-cache show wmanager
Maintainer: Tommi Virtanen <firstname.lastname@example.org>
Depends: libc6 (>= 2.1), libfltk1, libstdc++2.10, mesag3, xlib6g (>= 3.3.5)
Description: Select a window manager at X startup
wmanager is a small X11 application for selecting a window manager
at X startup. wmanager looks for a file named '.wmmanagerrc' in
the user's home directory which contains a list of window managers.
I didn't install it because I only work in wmaker now, but from the
accompanying README it seems close to what you're thinking of.