tb, I have seen joist housed into the tie using only a 3/4" pocket, after shrinkage there is not much left for support, 1-1/4" is a better number. Basically I got tired of cutting pockets in the side of the timbers and found lodging them on top a very efficient method. With the tooling I use in my shop I find a tusk or soffit tenon to be easier than a drop in pocket and it takes no wood out of the top surface of the beam like drop ins do. The peg needs consideration, though. So mortices in the face of the tie beam, I would use 22' long joist plugged into the mortices in bents 1 and 4 they are lodged on top of bents 2 and 3., spanning from bent 1-2-3 and a shorter joist covering the third bay. Alternating long short across the frame. Also the ties in bents 1 and 4 are raised higher than the two middle bents, so the tops are flush with the joist system, this fitting your visual requirements, almost. There is always a give and take, somewhere, here you get to have to two middle tie beam uncompromised with pockets and the end bents have stronger pocket where they are carrying far less load than the mid ties.
I hear you on the tie post connection.
