I was thinking along the same lines. What happened to Guile ( http://www.gnu.org/software/guile/ )? Maybe the developer(s) were not aware of it's purpose?
Substitute Lua with Tcl and it would still be underwhelming.
If this is successful, it would not be difficult to make a loader that lets it run Scheme. Of course, there are probably better Scheme implementations than Lua out there.