Ok, my attempt would also be to work with vanilla, and provide those to people willing to use a more recent "non-debian" kernel if they wish to do so. It's much easier to compile and deal with.
I was building with something like
make -j5 deb-pkg LOCALVERSION=-omvstone KDEB_PKGVERSION=5
soon to be changed to
make -j5 deb-pkg LOCALVERSION=-omvstone_amd64 KDEB_PKGVERSION=6
Hopefully omvextras will accept that. Outcome is the usual .deb collection of headers, images, firmware, libc-dev and debug-image. I incremented the pkgversion after each run (to avoid dpkg yelling at me) because I wasn't sure if I could re-install the .deb in a simple way otherwise without switching kernels, reboot, purge, install, switch, reboot. So far the simple dpkg -i for all packages worked without issues, plus the usual reboot.
Main problem from my point of view is to know/find all of those patches that are necessary/nice to have for most people in the omv-universe which are not in stable-vanilla. aufs was one of them, which was easy to copy and apply and configure (aufs4.1-standalone). Don't know whether there are other "vital" patches for debian and if they are a major pain in the ass to apply. And a correct config, of course
Edit: Just checked on those patches in the linux-source-4.1.6 by debian. Nothing special there for amd64, and besides aufs4, there is only grsecurity patched in which could be of importance for us. So I guess we're fine with vanilla then?!