So how much will it cost in money and out-of-service time to constantly repaint the aircraft?
Then you have the bigger problem of it being a military target with civilians on board. When soldiers adopt this practice of being out of uniform, they are treated as spys when in another country. What about a military aircraft in civilian colours? Is it a spy aircraft? This could be an excuse to destroy it anyway. Will there be more security for these particular aircraft and who will provide it? It certainly would be a potential target for people wanting to score twice against the UK. Once against the military and once against the "Capatilistic West" a la WTC.
They don't seem to have thought out all eventualities, do they?