Easy is pretty relative.
It would probably be "easy," but creating any
interface plugin for calibre tends to become quite involved
. At this point, I'm thinking it's probably not worth the effort for this small bit of functionality alone. Until such time as this functionality becomes incorporated into the "split" feature of MobiUnpack's core code, I'm afraid the stand-alone script will have to suffice. Sorry.
Anybody else is free to take up the cause, though!