So there is already a thing with Windows 11 where you can, as part of a Microsoft 365 subscription, upgrade your Windows 11 machine from Pro to Enterprise.

The idea of having the base OS be a subscription is really just a stones throw away.

… but the Pro -> Ent activation process is really a PITA and often randomly PC’s will revert back to Pro after they’ve been ugpraded, so I guess we’ll have fun with that.