As an aside, I have also been considering the idea of doing a
JavaScript implementation in CL, both to write more effective tests
for Parenscript, and to provide the option to run JSLint on the output
to generate compiler warnings (and of course to provide a JS
interpreter to things like the Closure web browser).

Wow, that's ambitious. Sound like fun, too, but lots of work. Might be much easier to create a foreign interface to spidermonkey, which seems like a pretty strightforward c library. Not lisp, but might be an easy win.

Adding analysis
to PS itself is another want.

What types of analysis are you thinking about?