Creating a UML profile for Lisp should be very interesting. It would be an excellent exercise for a lightning talk in the ELS 2010. It would be an excellent opportunity to test in depth the ArgoUML profile support. It would be a learning opportunity for me into the depths of the extensibility aspects of UML.
My idea is that it should have some common patterns amongst the several dialects and that those patterns should in principle be modeled in a reusable way in a common profile, maybe a PIM.
Then, each Lisp has a specific namespace system, macro system and library. This must be derived with a PIM to PSM transformation and then developed on its own.
A REPL for each would also be required.
A connector to connect to live Lisps to enable reverse engineering is also interesting. This is something that could take advantage of some sharing of a common base project, but, would naturally diverge for each Lisp dialect.