I think it would be really nice if it became possible to also boot a vanilla kernel. It wouldn't take much disk space and would help with solving/filing kernel bugs.
Since the vanilla kernel doesn't support squashfs at all, it wouldn't be useful for anything else, but that would not be its purpose anyway.
In addition, since burn errors are apparently often to blame for problems, an option to have the dvd check its own integrity might be handy. Ubuntu has something like this I think.

