Of course, if MASCOT had been specified correctly in the first place, they would be able to cross-couple the UHF and VHF frequencies so that, from a pilot's point of view, it would sound like a single frequency. There is a 'coupling' button on MASCOT, but the problem we found was the time differential between the signal being transmitted and ATC actually releasing the Tx button was so great that you ended up with an 'echo' effect which built up until you deselected the coupling!
Many civil ATC units (all NATS airifelds) have this facility, and it works!