Some of what's already put on the boot: line by default likely will fight with speakup; unless text as a boot: parameter is supported. Why not poll the keyboard for just the alt key being held down? If that happens, perhaps have ubuntu bing up speakup if it can with software speech at first. Maybe also not start up X at all automatically, and tell the user about a ubuntu accessibility directory on the livecd. If less or zless can be used, would-be users might find out how to customize ubuntu livecd before doing install say with a good ks.cfg file placed on a floppy. So long as boot parameters can be read from a ks.cfg file and those get described well enough this might be a possibility. If ubuntu can read a floppy with vfat format and read a ks.cfg file from it we're almost good to go.
