It seems like the answer to everything is PRS+.
I'm not trying to flame here, but as one who does not want to modify their firmware -- and has multiple readers, so modifying one doesn't help the other -- the PRS+ solution is... not!
One question I still haven't had answered is what is the default LRF font, and how do you select it for ePUBs? Without using PRS+ of course.
-Pie