Perhaps the reason the canon was never opened again after the days of Ezra was for the very reason that intertestimental writings ascribe diety to the messiah. Just a thought.
I really have to read the works in question before I can comment intelligently (or otherwise ;o). I've heard of extra-canonical writings that speculate about the preexistence of the messiah. Is this the sort of thing you are talking about? Or is it more specific?