I know all those exist and are possible. My point is that if you have a full stack of software already developed for pretty much all your range (like TP-Link do

I know all those exist and are possible. My point is that if you have a full stack of software already developed for pretty much all your range (like TP-Link does) bringing up a whole new one with Wifi drivers, NAT stack, etc just for the low-power device seems like way too much effort. I went and checked and couldn't find any TP-link device that wasn't Linux based, and they do sell very low end stuff.