Those RAID controllers, eGPU, etc. are not controlling other thunderbolt devices. If you know of any ARM-based computers with thunderbolt ports I'd honestly love to know about them. Like I said before, I've heard rumors of AMD based system with thunderbolt but never seen them in the wild.Huh?
What do you think is inside those Thunderbolt devices? They have Intel Thunderbolt controllers.
There are dozens of Thunderbolt enclosures for RAID. Those enclosures have an Intel TB controller. They also have a RAID controller from a company such as HighPoint. Those RAID controllers are all ARM processors.
I would love Apple to bring thunderbolt to the iPad. I just don't see it happening for a number of reasons.