VC-10 was (is!!) far more refined than a 707. I came back from Aden in a BUA one in 1967, a wonderful aeroplane. The reason for success of the 707 was probably more due to economics and the economies of scale. A certain colonial airforce ordered several hundred tankers of the 707 family. Now, if the VC-10 had the benefit of a launch customer placing orders on that scale history might have been different. I for one will miss her when the time comes for retirement, she certainlt is the Empress of the skies.
Agree that there probably isn't a practical re-engining option for the VC.
I understand that our colonial friends at Mildenhall sometimes position their tankers at Lakenheath instead of Mildenhall when crosswinds are unfavourable. Just take a look at how low slung those CFM's are.