Although it might seem cool, there are a fair amount of issues with this. For one, Druids already have shapeshifting, so this idea of magic is fairly covered by that. Second, if a conjurationist were to target themselves as the location to conjure, they'd be unable to cast inside of their body without messing up. Even if they managed to do that, I doubt they'd be able to keep the focus and concentration on keeping the conjuration there, let alone it being a long term thing. It's a neat idea, but it just doesn't work with any of the lore at the time with how it works.