Flyinkiwi,
Working from increasingly long memory (so I could well be wrong), but the cockpit layouts of the A and the B are very nearly identical, with just an additional 'mode switch' on the left hand control inceptor ('throttle'). However, there are differences in the cockpit display software to support STOVL operations. The view forward is the same, the view aft isn't.
MSOCS is absolutely correct about the simplicity of flying the F-35B compared with the Harrier, and I'm sure that the amount of hours required to adequately train pilots in the basic mechanics of STOVL takeoff and landings will be very low.
However, where there will be a delta will be the training required to allow pilots to operate safely in the totally different environment of the carrier and its associated fleet. All the way from responding to mandatory instructions from flight deck crew to the completely different arrangements for recovering a formation to the fleet and the ship. However, I don't want to over egg these aspects - naval aviators have been doing them for some time, and the FAA has enough continuity from its exchange time with the USN to redevelop those skills.
On the practicality of a split fleet, it might help to appreciate where the major technical cost drivers are in supporting a combat aircraft. In my experience, they are avionics, propulsion and airframe systems. F-35A and B avionics hardware fits are very nearly identical, and there is a very large amount of avionics indeed on any F-35. On propulsion, I am told that there are some common components between the A and B engine, but there are a lot of unique B components associated with the lift system. Airframe systems have a great deal of commonality between A and B.
Again just my experience, but the actual airframe bits (frames, skins, etc) are not significant cost drivers.
My own thoughts (and that's all they are) is that it would be nonsensical to buy 138 STOVL aircraft if the standard assumption for the carrier is 12 aircraft at sea. I'd suggest building a fully joint support and training system that delivered As and Bs (and trained aircrew and maintainers) to the respective Services for their operational tasks - to the RAF and Air Command for land based strike and recce, and to the RN and Sea Command for maritime strike, recce and fleet air defence.
Hope this helps the discussion along - best regards as ever to those working in the puzzle palaces,
Engines