reading around the kexec / atags issue it would appear to require the atags support adding into the kernel at build time. There appear to have been various valiant efforts to circumvent this on various devices but I have yet to find a success report.
Of course that doesn't mean there aren't any - just didn't find them yet.
Did find this http://forum.xda-developers.com/show....php?t=1522024
for a Gen8 Android device, which while not a solution, IS an interesting idea. However I don't expect many end users will fancy a bootloader, however for those daring few it could be helpful (as an idea, it's based around buildroot so may be transferable)
So anyway, I'll revisit this when my brain works.