Possible, yes.
Desirable? Maybe to a very small niche group of users who might be willing to take the effort to make it work. It would also go against Apple's core philosophy of simplicity and minimalism.
I don't see Apple making one, and not just because they would rather you buy 2-3 separate devices. It just doesn't fit with their overall vision, and it's not something the majority of users are going to need or want. At the end of the day, it all goes back to their grand theory of Apple, where the job of the iPad is to take on laptop tasks, while moving to make technology smaller and less confusing.
A dual-boot iPad / MacBook hybrid is the very antithesis of everything that Apple stands for. I think the design team would sooner burn Apple to the ground than allow such an abomination to exist.