Miller Says Yes
https://www.weldersupply.com/Content/files/PipeWorxRemoteFeeder%20-%20Copy%201.pdfHow effective depends on what you are welding eh?
How will you accomplish fill and cap passes ? With Co2 you will not get a spray transfer. Will you switch to FCAW for everything but the root?
How the C02 performs on the root will also have a lot to do with the base metal type, if impacts are required and more.
I suppose a dual feeder GMAW setup with solid wire on one side and FCAW on the other could do a very good job on pipe... RMD for the roots and FCAW on the fill...... All with Co2 weld gas. It's possible.
If you are in the "shopping stage" I would just ask Miller to bring a RMD power supply into your shop and prove what it can do before you lay down the money.