Eric's original question was whether he could take a standard RFM with a straight blade, use it for cutting lawn, then change the blade for a spindle pan with free pivoting blades when it was time to cut the hayfield. My answer to him was, "No, you cannot simply take the straight blade off a standard RFM and stick on a RC blade and make your own hybrid." He wants something like that vehicle that changes back and forth from SUV to pickup truck. The Woods RM990 seems like a great compromise, but my point is that you cannot change blade types back and forth.
I like this model. It will meet the needs of people who cannot afford a finish mower and a rough cutter (although I think most people who can afford a tractor with enough hp to drive this thing could afford 2 cutters). A disadvantage I would see is that weed seeds picked up while cutting in the rough could be dropped into the lawn unless you power washed the underside after each use in the rough. It's also very wide to maneuver between trees and shrubs in the lawn.