Do you happen to know an embeddable Lisp that can easily bind to C++ objects (rather like AngelScript or luabind)? I too would mostly rather a Lisp, but doing all the plumbing sucks.
If Lua's semantics are acceptable, you can make a loader that runs your Lisp in Lua. This is probably less effort than it sounds like. Moonscript is a decent example of a mostly expression-oriented language as a Lua loader, so it should be simple to make it read a Lisp instead.
Interesting approach, thank you. I don't much care for Lua (either as a language or as an API, especially when dealing with C++), but this is a pretty neat concept to think about.