How many adversaries have the ability to act on that risk? I hate the security defeatism that is rampant across the space. The perfect is the enemy of the good and all that. Unless your threat model includes nation state adversaries (or individuals/orgs with similar levels of skill and funding) explicitly targeting you, worrying about IME/PSP is probably completely unwarranted. Unless I'm unaware of active exploitation campaigns against these systems, in which case I would love to learn more.

Edit: Don't get me wrong, I would love to see a world where the entire system is open from hardware on up. Unfortunately I don't know that we'll get there without some substantial shifts in humanity as a whole.