NAB, I am not sure that 'Trust me I'm an engineer" chimes any more comfortably than "Trust me, I'm an accountant". I have known many of both and as a sweepingly unfair generalisation, I have found the former to be overflowing with boundless optimism, sometimes well grounded but equally often not, and the latter, well, it's sometimes difficult to know what they overflow with. But any project of this magnitude needs some of their respective disciplines to migrate in each direction.
I certainly agree if unlimited funding and unlimited time is allocated to unlimited engineers, then F35 will exceed expectations. But that's where the accountants will probably have to spoil things again. At present F35 will deliver unknown capability at an unknown price at an unknown point in time. I don't make personal purchases on this basis, but I might be tempted if I had an unlimited income stream from taxpayers to fall back on. - well that's the way it used to work until the bankers overstretched a bit and reality made a comeback.
I defer to your engineering expertise which dwarfs my understanding of such complexities, but if I were a decision maker on this project (you will be relieved to hear I am not) I don't think I would be saying "Right-oh, just let me know when you're finished and send me the bill" - and I don't think you think that either. People do have the right to ask such questions and get answers - except we are not.
And I agree all complex systems grow into their capabilities. But that means that we might have a small operational F35 fleet by say, 2025, barring major setbacks or politics, about 30 years after the project was born. That's a long time to wait - let's hope our enemies will be patient enough to wait for us.
On a personal level I still believe the risks surrounding F35 are far too many to commit to it - yet.