I like your basis points... I also like your connective points.
One thing you left out: Volume. As in, volume of information Natasha dumped onto the Internet. Who's going to have time to sort through all of that? And, of those who do, how many of *them* don't already know Coulson is still around? And, how many of those interested parties would have been Avengers.
Maybe. But, I'm sure he would have been far more interested in the tech.
As for Thor, the "volume" with which he deals is details. The details of keeping up with The Warriors Three; Sif; the death of his mother; the irritating occasional debilitations his father endures; dealing with Avengers' stuff -- it's possible the subject never comes up when he's with Heimdall. Why would Heimdall bother Thor with a detail like that... he probably already told Odin and that would be plenty. He and Thor aren't drinking buddies, after all.
Clint doesn't appear to have any relationship with Mockingbird in the MCU - that position went to Lance Hunter who is the TV side's "replacement" for Hawkeye who, himself, now has a wife (who is not Bobbi Morse) and 3½ kiddos.
And, Natasha has her own issues (Cap's decommissioning of S.H.I.E.L.D.; Fury's death-not-death-"retirement"; Ultron; Bruce Banner...)
These guys are good, but, unless they *know* to look into an issue, they may not even realize said issue even exists.
But, I like your postulations. And, I like the way you presented them and the fact you took the time to write them down for us. Thanks for that. But, I still have my dreams of Coulson walking in on the Avengers and saying he's been stuck in "Level 8 Hell" so hadn't been able to join them in a while.