The main question I have concerns the Plate - Tie connection.

If this were a typical English Tying Joint, where the Plate recieves the Tie, then there would be absolutely no problem with assembly,

my schedule would go something like,

* Braces are assembled (if they in fact meet)
* Posts are slid onto the Braces
* Plates are Dropped onto the Posts
* Ties are Dropped onto the Plates.

And,
if the Plates recieve the Ties, then,
the last two steps would be;

* Plates and Ties are assembled
* Plate Tie Assembly is dropped onto the Post Tops.

If the Diagonals are running in a slope I would agree with Jim, and use Brace Tennons, though, longer than the typical 3" used in many shops,

If the Diagonals are running in a level Plane I would just use a typical Mortise and tennon joint, maybe 5" long, to provide some relish.

With 12" x 12"'s you have more than suffient room to provide any number of housing schemes and, long enough tenons to act in tension.

I really don't think you need a model, but, if there is a question of design, there is nothing wrong with creating a section and an elevation, yes?

Tim Berube