A Robox (CEL) printer was gutted of the propriety electronics and revitalised with a custom right-angled filament feed head, throat cooling system and print cooler. Using old parts, like a Pentium heatsink and various other scrounged stuff, this machine was bootstrapped by having to build its own printed parts. A Mega 2650 with Marlin and Octoprint has made a very useful if not feature complete rescued 3-D printer that definitely had good hardware, but had become too expensive to maintain with over the counter original parts.
Recycling old printers with better electronics and hardware will become as important at recycling the filament in a world of finite resources.