LO,
Thanks for coming back.
Yes, I agree that the decision to go for basically a common airframe drove an element of risk into the programme, but one of the aims of the JIRD/JORD process was to get sufficient convergence of the key performance requirements around a single engined single seat design. As I've posted before, it's my view that the Pentagon used STOVL to keep the aircraft single engined single seat to control costs. It's worth remembering that they were coming off the back of a series of major (and really costly) project failures involving large twin engined tactical strike aircraft.
There were a number of emerging technologies that were used to achieve the aim - these included a very high efficiency and very powerful engine, the F135. I can tell you that the engine has met its weight targets, cost I can't comment on as I don't have the figures to hand (GAO reports provide good data on this).
You are absolutely correct that the drive for manufacturability was driven by through life cost targets - but the problem was that LM failed to properly hoist in the fact that a powered lift aircraft cannot compromise on weight. Not ever. Not at all. Never. They had no excuse for getting their weight estimates wrong either, as BAe had offered (and briefed them) on all the lessons they'd learned on Harrier as well as Typhoon. These were pretty brusquely dismissed by LM.
At some time in the future, there's probably a good book to be written by insiders on the F-35 programme on what went right and what went wrong.
Best Regards as ever
Engines