VC10 was designed as an 'Empire' transport, when Britain had more colonial interests, overpowered to get in and out of hot and high airports with relatively short runways, runways have in the most part been lengthened and mounting engines high and out of the way of FOD was innovative and successful then but unnecessary now.
Fuel burn is going to be higher as the aircraft structure is heavier than the ideal, 2 engine pods mounted on the wing is the optimum solution as demonstrated by virtually every modern airliner in production.