One imagines that the cost of dragging F-35s across the Atlantic/Pacific on internal fuel only will soon enough start to overtake the development cost of a bog-standard tank...
Using open source figures for the F-35B internal fuel and guessing at the transit burn rate, fuel onload rate and refuelling burn rate, I had a go at a trail plan using Autumn 75% stat met to trail 3 x F-35B from Halifax to Marham at FL270. The system reckoned it would need 5 brackets and a total offload of 33.4 tonnes for the 5:45 hr flight on the Northern Route - with abort aerodromes at Gander, Narsarsuaq, Keflavik, Prestwick and Leeming. For the tanker type assumed, 78% stat met was the absolute limit for 3 x F-35B, but if only 2 were trailed the normal 85% stat met planning assumption was do-able
So are external tanks really needed? Organic shipborne AAR for the QE class would seem to pose a problem for blue water ops though, given the constraints of STOVL operations. A single role tanker configured V-22 would seem expensive for such a 'one trick pony' role and could probably only offer around 8000 kg offload from a single centreline hose, but what other options exist?