My preferences in resolving some of the same issues is to just have something more akin to a GRUB shell available; this is hard for N800/770, of course, as we have no keyboard, but it should be possible. That (in conjunction with using bootmenu.d) also makes it easier to add and change the bootmenu, as well as providing dynamic recovery in the horrible case of having a non-bootable mtdblock4, and having just SSU'd a working mmcblock0p6. You could flash a generic bootmenu, and try things till it boots, just like a GRUB floppy.

Stskeeps, what you're doing looks excellent so far; I might work on a patch for live editing (at least for manual selection of a new entry, if not rewriting the config file; I'd rather not attempt that until I think it over more and until I know the bootmenu.d stuff is finalized and approved for release... ). The main problem I see is that an on-screen display using the d-pad to select letters one at a time is going to be infuriating to N810 owners, and without an N810, I can't really attempt an implementation using the N810's keyboard.