Although I disagree with you, you have laid out arguments better than any “Pro-kafor” person I have talked to.
I think the main place that “No-kafor” people would disagree with you is on the positioning.
While Noel is athletic enough to chase stretchier fours around the perimeter and tall enough to deal with traditional ones, he doesn’t have the offensive skillset to play there. He would be best utilized as a classic pick and roll dive man with shooters spacing the floor. This is made much harder with Okafor manning the block.
In a similar way Simmons could lineup offensively as the point but not defensively. This is why a guy like Jerryd Bayless makes a huge amount of sense for the Sixers, he is a point guard sized guy who has more of a shooting guard game. Allows him to cover the point, while Simmons can defend a forward position. So even though Simmons could functionally play point he is still playing either SF or — most likely — PF on one end of the floor. Saric is almost identical in that he could be a wing possibly on the offensive end but looks limited to guarding the worse of the swing-forwards in most matchups.
You are right that Okafor is definitely a center but his atrocious defensive rebound rate and limited NBA skillset lend him to best be utilized as effectively a DH off the bench to beat up second units. But this is a role that he and his father don’t want him taking on a team that isn’t “winning”. A great catch 22 because it would be pretty hard to win with Jahlil as your starting center.
As for your thoughts on Embiid, yes, it has sucked that he’s been super injured. But he still has tremendous upside and even if he plays limited minutes and plays decently probably drives Jahlil’s trade value down because the “log jam” is even more apparent. Embiid would also most likely be center limited and Jahlil is likely to want 30 minutes on a “bad” team. Those minutes won’t be close to being there.
Finally, Colangelo said it himself, that one has to go. And in reality it doesn’t matter what either of us think, or Tjarks for that matter, just what Colangelo/ownership/Brett Brown (maybe) thinks. Do I think they should just dump Okafor, no, but they won’t ever get that much in return for him. Offense from the center position is much less valuable that defense from it.