This sounds very much like the problem with creating distro kernels that came up several weeks ago. I don't see why a similar approach couldn't be used here.
something like what Alan Cox listed
> However providing you separate the initial profile from the later tools
> it simply becomes
>
> make distroconfig
> [cp /etc/system-kconfig(.$ARCH?) .config
> make oldconfig]
seems like it could be adapted very easily (while providing useful functionality for non-ARM systems)