If someone at Apple is reading this, please, for the love of god, let me pay to have iMessage on my windows machine. I'd easily pay $100/year.
iMessage is not its own subscription service yet, but the days where it was explicitly an Apple hardware moat may be drawing to a close the more that Apple finds increased relevance (and shareholder appeal) in software as a service. I expect that if that were to happen, Apple might try to make a good marketing effort of "works best on Apple hardware" and Apple might never support iMessage on Android, but Windows support sounds oddly plausible in 2023.
My iMessage bridge is hosted on "Beeper Mac #84" according to my Apple account page which shows logged in clients.