I suspect it's not the kernel, but init/udev that's starting raid.  Try booting with init=/bin/sh or /bin/bash or whatever shell you have in initrd, and that should get you a shell prompt without any of the userland initialization.  It won't even have the root filesystem mounted, probably, but starting from that point, you can assemble by hand any arrays however you like, mount root, and whatnot.  It is a bit inconvenient to use, especially if you should need binaries or libraries that are in the root filesystem only, but PATH and LD_LIBRARY_PATH are your friends.