You mention debugging the live Deep Space probe using a LISP REPL, and I remember reading somewhere else how people troubleshooted an earlier Voyager (?) probe via a FORTH REPL. Were those schools of thought in contact at all?

What do you think about the efforts of some Haskell folks to make embedded languages that would generate code for a more limited system but at the same time leverage the beefy Haskell stage as both an extensible static analyzer and an overgrown macro processor? There were a number of those (I think shaders for earlier-generation GPUs, real-time control code, and even hardware synthesis were all among the attempted targets) and I don’t know that they got any adoption at all, but this sounds similar to what you’ve described doing on less capable machines with LISP.