Wow! That is a thing of beauty, I like it.

Engineering fee will be high:

Check for uplift at the outside corners
Check the size of the corner crossing ties
Heavy load at the ends of the crossing ties
Check shear in the through tenons

phew...that gets complicated, its sort of like a hammerbeam truss except there's no buttress or big ass post to anchor the outside.... on the other hand you could argue a well fastened roof diaphragm could do much for this frame...

but its very creative...looks great!