I also forgot to add that you may need to chmod +x /usr/bin/wmxfce - shouldn't if it was copied from an executable; but it might be necessary as I haven't tried it in practical application on this yet...

To add an icon the panel you can do one of two things.. Install Personal Menu; go into the Control Panel; and edit "Personal Menu"..

The other thing is to copy the /usr/share/applications/hildon/debwm.desktop to something like /usr/share/applications/hildon/wmxfce.desktop .. Edit it; and change the Title and Commands to their respective ones.

ETA: I did some googling and I think the command is actually xfce4-session .. not xfce-session... so try that one inside of wmxfce..