The drive electronics on the budget machines have no easy way to add feedback mechanisms. So you'd somehow have to either roll your own driver electronics or do major surgery on the existing board. Since I don't actually have a feedback issue at all right now I'll just leave it as it is but if this becomes an issue I will definitely look into it. I still have a small form servo set + drivers laying around from another project so it isn't as if I'm wanting for hardware. And it would be nice to finally put that to use, even though it is probably a bit much for this machine.
I haven't encountered other happy customers of it, but for a bolt-on closed loop upgrade I'd recommend MKS SERVO42 series. It's a hobbyist type product that comes from AliExpress no enclosures or safety protections, and slots right into RAMPS driver ports. It just needs an initial calibration, no software changes needed at the host side.
