Haven't read the entire thread yet, so hopefully nobody has said this:
Perl, write-once, poor choice for uncontrolled environment.
Lisp, at least the computer science type will know. Haven't used it
myself since early '80s.
Lua, don't know whether it's improved in the past few years, but freeciv
had serious problems with migrating to 5.1. Personally, I've given up on
it, but my 14 y-o nephew seems to like it for various game modification.
Everybody seems to be going the python direction lately, but I've only
minimal experience with it, so cannot make a recommendation.
I'd worry less about providing extensive functionality (we certainly
don't have much now, so anything more would be gravy), but rather
ease of integration, scalability, and security.