I think this is the most realistic approach mentioned here, and tromey is actually familiar with the Emacs internals.

So is BT Templeton, the person who has been hacking away at Guile-Emacs GSoC after GSoC. :-)

(They seem very skilled, don't be fooled by the fact that it's GSoC; no idea what the skill level of people who take part in that usually tends to be.)