Out of curiosity, what in ARMv9 are you looking for that isn't either optional or already mandated in ARMv8.5? I'm actually not sure what ARMv9 additionally mandates over ARMv8.5...
SVE/SVE2 is optional in ARMv9 [1], despite all the reporting claiming otherwise.
Y’know, now that he mentions it: no cooling system, no ventilation, and takes up less rack space than a Mac Mini. Probably will have Thunderbolt 4 ports and you can route power and data through one of them. MacBook Air Colo, I can see it.
Except you're paying for a screen, keyboard, and trackpad you'll never use. Mini's are much more cost effective.
An M2 Mini with a 10G port... I'd be really tempted to buy a few.