Some above have joked that the only modification should be a large water boiler for the tea, my view is even this is a step too far and the aircraft should use airline style beverage makers that can be overhauled by the airline maintaince system ( no doubt at 10% of the price of any bit of equipment designated as defence
Quite early in the Sentry's service, the aircraft water tank was deemed unfit for consumption due to a build up of bugs, and replacing it would have been expensive. The aircraft coffee brewer was also deemed unsuitable as it leaked over the electrics and was removed early on in the aircraft's career. The result is that for many years the crews have relied upon bottled water which was heated up in a plug in container which takes ages to bring up to temperature (first on board - fill up the hot-jugs and switch on). Far superior was the Shackleton's water boiler, filled by pump from a large jerry can (not withstanding the day that the boiler once broke on the start-up for an air display and it wouldn't turn off. Cue to the sight of a Shackleton taxying out, disgorging clouds of steam through the beam window with one of the mission crew pumping away to ensure that the boiler did not run dry).