I remember the first gentoo. On the framebuffer it had a beautiful blue/gray background with the logo and provided you with choices. You could build everything from scratch or install a bootstrapped version. I tried both, failed and gave up (my poor AMD k5 couldn't handle the heat). But the point here is: it was always easy to build a kernel within your debian installation from deb-src. You could even build it as a deb, install it and reboot into it. If my job was to manage a linux kernel, I'd have a script which took the latest sources, set kernel parameters, packaged it as deb-src and then it is just two steps to build and reboot. Then I could switch between them easily.