I'm not sure what the point of this really is. Many of those printers and POS systems have OpenCUPS support already, which is more or less "one command". If it requires a Raspberry Pi I have no idea what you are selling. Can you please elaborate on this?
I've got a bunch of thermal printers in my work lab that definitely don't have this but they all support ESC/POS. They're all currently produced kiosk style printers.
Valid question. Printercow is aiming for a plug-and-play scenario where you can use whatever thermal printer you want with an extensive html-like template engine.