I'm actually trying to work on my own DE as well. It'd be fully scriptable
and modular, and allows for the replacement of any part of it with another
part (say, XFCE4 panel with GNOME panel, or Metacity with Emerald, and so
on).
Right now though I'm still working on it and deciding how I'm going to go
about releasing it. I use it on my main desktop PC running Parabola, and
while it's proving to be very stable, I need to make it less 'hacky'.
My goal is pretty much create a 'base' that would install the necessary
scripts and whatnot, then require the user to modify a config file to specify
the components they wish to use for what. For example, a layout might be
XFCE4's panel, Docky, Nautilus, and XFCE4's Terminal as the base
applications; or another would be LXDE's panel, no dock, PCManFM and XFCE4's
terminal. Maybe at a later time, I might make it graphical, and automate the
installation process, making it easy for anybody to use. I basically want to
make a sort of desktop environment that would allow the user to choose what
they want to use.
Just thought I'd share since we're talking about DE shells.