The opportunity ought to have been taken in the 1990's to design and build an entirely new, purpose-designed aircraft for the roles required. If Portillo, the Defence Minister wot signed the contract, had taken an interest in aircraft instead of choo-choos, he would have known that every scheme cooked up by Air Force and manufacturers the world over to "modify" an existing type in order to save money, doesn't. Redesign leads to retooling leads to a creeping realisation that for an extra x lbs of airframe, y capabaility is possible. And of course, x lb airframe costs £ z000. The end result is about 95% different but which will still become obsolete at about the same time the manufacturer's order book tapers off.
My dream would have been to start with a clean sheet of paper or monitor screen. Add to that the requirements of the roles such as: full-spectrum sensor suite, long range, capacious weapons bay, roomy cabin for sensor operators and we have the beginnings of an aircraft.
But why bother with the conventional fuselage, wing and tail layout? Wouldn't a blended wing body design offer more room, greater structural strength, less drag? Imagine the Avro Vulcan or Armstrong Whitworth AW52 and bring them sixty years up to date as something like the Boeing X-48.
Look at the internal volume offered by a blended wing aircraft: