yes there is now officialy a central support
not a post but a masonry chimney
there will be flat steel rings around the circumference where the rafters(hips) bear to take the weight and steel pins will be welded or drilled into the ring for fasteners...just like earthwood.
it may be architecturally uninteresting but central masonry chimneys are very nice in a canadian winter...

as far as the dragon beams go, they do look good on paper, the designer likes them, would we be wasting wood and joinery time to use them? It's hard to see how the beams could escape once you place those ties down on them.

And, as far as daps go, are you thinking of a horizontal lapping of the beams on top of the post? i assume there would be a tenon of some kind rising from the post to index the joint?
the problem with this joinery is that one beam would be cut from the bottom up and this is bad for weight bearing timbers....do you have a way to half lap and get the bottom of both beams on the post top?
questions questions questions
i hope i'm not the only one benefiting from all these questions
a thousand thanks
-Mark.