It looks like a very interesting idea, and would certainly be very valuable if we can actually get it to work. But some of the issues you mention do look difficult.
Does Psyco itself have any documentation that discusses their implementation? It might be useful for finding ways around the difficulties in writing an "arco".
"Possibly this could make a good Arc Summer of Code project?" Yes, probably. Well, actually I don't know how these things work. At all. But I guess it is...
Edit : yes, I think that would be a good idea !
Btw, yes, these are really hard problems I think. It won't be done in a few hours. However, in our case, we already have mzscheme doing a good part of the work (it could be interesting to get even closer to the bare metal, though, but that could be done later). Psyco, on the other hand, compiles down to assembly code.
I found a few references about how Psyco works, I'll give back the links here next time I use my regular machine.
I'm pretty heavily involved with LispNYC, and they're the lispiest of the Google SoC sponsoring organizations. I'm also pretty interested in psyco, so if someone finds a student who wants to work on this, I'd be happy to mentor.
