Mmm... for the magic, in Shadowrun magic is very much academic and theoretical as it is inherent and a talent, so even if he gets the spells he'll have zero clue what to do with it. 

If the problem is him becoming a giant dragon, well, he's still mortal and he'll still probably die to normal weapons or to things like wicked weaves easily, if you're worried about me going berserk with him. There's also the fact that Joseph has to get used to the fact that he has wings at all first before attempting anything. If anything, Joseph as Great Dragon would be extremely clumsy and awkward.

Also, Dunkelzahn's dragon form isn't really that big - that picture is just an appearance; not to scale. In Great Dragon form he'll probably still fit into something like the stage of an auditorium.