That was my original idea, but it seems not to be easy to do. I experimented quite a lot with the vanilla Nokia kernel, both to use kexec as module and as compiled-in feature but the results were not very good. With the Nemo kernel it is lot easier.

With this method I am using, all you need is to flash the first stage kernel just once, and any of the second-stage kernels can be booted from a directory in the filesystem.

You can have multiple kernels running on the same filesystem, just by starting them with a different command line; for example I have both the nitdroid kernel (running the normal way of chrooting it to /home/nitdroid/) and an own flavour of openmode Nokia kernel, either one can be launched from a file on the FS.

Also, as the selection is done before booting the final kernel I can rearrange partittions as I like, mounting for example Nemo partition as root and launching the Nemo kernel.

Nothing would prevent me running Debian, for example using my Harm-Chom-install image, mounting it as root and starting a kernel of my desire on it. (I could do that, but there is no point really as of course it would not use the phone functionality)