The thing with the F-35: if you're in a visual-range turning dogfight with an F-16, you're probably screwing up badly (or restricted by an exercise). The F-35 gets info fed to it from AWACS so that it doesn't need to turn on its radar. Its mission is to use its stealth, come in high and fast, and fire a missile that the enemy doesn't perceive until his jet explodes.
The CAS tank-killer mission is completely assinine and will never be flown. When aircraft are justified before congress, they have to promise to do everything and they have to "prove" through testing that they can do everything. When they can't, the media just rips them apart, which is exactly what has been going on. Using this platform to fly the A-10's mission is a complete joke. If it could, the Marines would've slapped a 30mm gun pod on the AV-8 Harrier and had been flying that mission since the early 1980s. The Air Force tried that on the F-16 in the early '80s and the results were horrid, as any normal person would expect.
Missile lock on a SR-71? Like the time over Libya? Where the guys floored the bird and watched the missile fall harmlessly into the sea far behind?
Getting missile-lock on a SR-71 and hitting it are two different propositions.
Somewhere here likely I read that the standoff missile the F-35 is supposed to be armed with is too big and too heavy. So that leaves the handful of rounds in its main gun. Very useful; worth every penny, etc.