BigDaddyBoxMeal
Are you sure the VCCS is actually cross-coupling the frequencies, ie a call received on one freq is automatically re-transmitted by ATC on the other?
From what I hear (or don't hear!) from a nearby ANSP who operates TWR/APS they have operate with a cross-coupling system. Echoing the sentiment expressed by Hotel Tango, wonder if the relevant hazard appeared in the risk assessments? If cross-coupling is not mandated I would speculate that there would have to be some quite innovative mitigation developed to get the risk down to ALARP!
Haven't yet met a cross-coupling system that effectively does it. If you know of one I'd appreciate a PM.