I don't support Multiboot because it flashes the kernel each time you want to boot something different. This, combined with the limited writes of flash memory -- and that the kernel partition has no wear levelling -- means that I don't like it on principle.
U-boot is what I'd like to see used instead, but apparently the Nitdroid folks aren't willing to change. And so, I won't install it until multiboot's removed, which may be never.
As far as adding support, I really don't like adding things I can't test myself, but after seeing what's needed(no edits to my script, one pre-written menu item file added) I'm willing to take a chance and make more people happy. Also, i'd be able to track multiboot users as well - see how many use it versus bootmenu.