someday I hope they actually make another rack system....
Pretty easy to get minis or studios into racks with 3rd party mounting solutions. You do need to pay attention to power needs (low, but you need AC power, not DC) so might need a PDU in the rack to convert / distribute depending on how many you're planning to put in each rack.
Indeed, it’s not out of reach and compute density is higher than the Mac Pro with Minis (even the core i9). M1 / M2 is vastly higher.
The current Mac Pro (M2 Ultra) is available in a 4U configuration,[0] but you’ll pay a pretty penny for it. It starts at $7.5k.