I know of no way to do a 'merge' of kernels.
Incidentally, I wonder if this is one of many reasons to make editors write to 'project' files rather than the end-result binaries. With a 'project' file, we can record revisions and authorship, we can tag certain changes as 'linked' to specific kinds of mods (so we can 'switch' elements on and off for different builds), and exploit a whole host of other miscellaneous features.
Thoughts?