Might it be useful to think of a Cocoa application as a special kind of Lisp system? If we had a ProjectBuilder sort of GUI for working with (ASDF or DEFSYSTEM) Lisp systems, then we could also use it to work with Cocoa applications. COCOA-APPLICATIONS could have additional file types associated with them, and could also responsd to a SAVE-COCOA-APPLICATION operation (perhaps by starting up another OpenMCL with a command line option set to load in the specified system and then SAVE-APPLICATION).
Yah; this is a good idea.
One other thing that might be interesting for someone to look into:
F-Script (http://www.fscript.org/) allows a "live" interpreter to be embedded inside Interface Builder, allowing interaction with UI objects in Interface Builder (see http://www.macdevcenter.com/pub/a/mac/2002/07/12/embed_fscript.html? page=3).
I wonder if it might be possible to use similar tricks to get OpenMCL talking directly to Interface Builder via a remote REPL, allowing a very tight interaction between the two in building GUIs.
Randy