There's no reason to assume a private email server is inherently insecure. If it was properly hardened, it's a non-issue from a national security perspective.
Hell, given the old tech the government still uses, a private server might be more secure.
It would likely open up the market for arm motherboards, since they're not the only player in the game. I think it would ultimately be a good thing, but it would probably take a decade or so to truly compete with x86-64.
Apple opening up the market would definitely give the process a kick in the pants.