ORAC (and others),
Perhaps I can help a little here. I was part of the weight reduction effort for the F-35B. To the best of my memory, the plumbing for external tanks on the inboard pylons was NOT removed. I don't remember it ever being offered, as the requirement for the capability to carry what were often referred to as 'ferry' tanks was clearly stated in the Systems Requirement Document (SRD). When I left the programme a long time back, that hadn't changed, as far as I remember. If I'm wrong, or if this has changed since, I apologise in advance. It's true that the requirement to develop and integrate the external tanks was subsequently deferred and may have been cancelled since. But I think the plumbing is still there.
I don't ever remember a centreline tank being seriously considered.
In the very early days when they were introduced in WW2 for escort fighters, 'drop tanks' were specifically designed to be jettisoned on all missions, when empty or when combat was required. Fairly quickly, especially on naval aircraft (e.g. Corsair, Hellcat) the 'drop' tanks were often retained on the aircraft - it's possible that the problems of shipping more tanks to the ships influenced that decision. Since then almost all 'drop' tanks on tactical jet fighter bombers (land or sea based) have not been designed to be 'dropped' on a regular basis. What they actually did was to solve the basic limitations in range and endurance common to almost all tactical jet aircraft. 'Drop' tanks are an easy fix to the conundrum of how to carry more fuel when there's no space left inside the airframe.
The F-35 never required drop tanks to allow it to meet performance requirements, which is (probably) why the designation of 'ferry' tanks was used. If the RN (or USMC or USN) were to come up with a need for using external tanks on board, I'm fairly certain that they would embark one set per aircraft plus a few sets of spares. I would also offer the view that the size of the QE class would make stowage of extra tanks a fairly straightforward issue. A standard technique is to hoist them up into the hangar deckhead (ceiling) on a special cradle. There seems to be a bit of room for that option on the QE. We certainly managed it on the CVS and than was an extremely small ship.
Hope this helps the thread, best regards as ever to all those doing and redoing the range and endurance calculations as things change,
Engines