I think that a decent solution for 11.04 would be to create a
temporary workspace for the fullscreen app so that it shows in the
Expo (Workspace switcher) mode but once the app is un-fullscreen-ed it
would return to the workspace from which it originated (no fancy
animation transitions). Alt-Tab-ing while the fullscreen app is
focused would tab-between workspaces and not applications. If you
alt-tab while a non-fullscreen applications is focused (so you can see
the launcher and the panel) would tab between applications that are
currently open and the fullscreen apps.