In fact, there is already a Lisp (Common, not Emacs) tiling WM called StumpWM.
If you haven't heard of it yet, it's partly because the Lisp community isn't so embarrassingly insecure and desperate for anything they can pass off as a "killer app" (see Macsyma or Emacs itself) that they feel compelled to shove it down everyone's throat.
If you haven't heard of it yet, it's partly because the Lisp community isn't so embarrassingly insecure and desperate for anything they can pass off as a "killer app" (see Macsyma or Emacs itself) that they feel compelled to shove it down everyone's throat.