In your scenario you're basically trading procurement costs for operational costs. Operations and maintenance account for 75-80% of the total life cycle cost of a system and you're talking about consistently sending 3-4X as many aircraft to do the same mission. Not to mention that in certain high threat environments you have a higher probability of losses including losses in the most valuable and least replaceable part of the fighter system, namely the pilot.
Loosing half of twelve F-18F's or loosing half of four F-35's ? I'll take my chances with six F-18F's over two F-35's.
The maintenance costs of a F-18F are much lower than F-35 service.
While the F-35's are on the ground with highly trained techs nursing complex systems. A bunch of farm kids have the F-18F's flying.
That's where the high/low mix comes in. For high risk missions in contested airspace, you have a smaller number of F-35s that have a higher probability of surviving the mission just based on remaining undetected. Then for lower risk missions which comprise the bulk of any operation, you have a higher number of Super Hornets. You get the best of both worlds in the form of increased operational capability at a lower total lifecycle cost.
F-35 and F-18F are built by two different manufactures. Now twice the training, tooling and spare parts are required $$$
The F-35 can't get anywhere without tanker support. There is extra upfront cost,, overhead $$$ logistics and vulnerability
The Hornet upgrades in development are nice and have decent front aspect stealth from all reports, but you won't ever get the same level of performance as you get in a purpose built design especially in side and rear aspects, which are the issue in heavily contested airspace. They're a great low end complement in the high low mix but unless you're happy losing pilots, I wouldn't bet the farm on them.
The F-35 is not invisible to radar. It has a exhaust plume that is detectable. Depending on the range and radar frequency any and all aircraft show on radar. There is no radar invisible airplane. Then there are contrails under some conditions and plain old visibility by eye.
Not that easy. Multiple variants increases costs in a variety of ways. Start making major structurual modifications like new wings and you'll erode the benefit you get from using an existing platform. More than one program manager has fallen into the trap of "just using existing system X and make a few changes" only to have the whole program crash and burn.
It's only a wingtip and the engineering has already been done. They just bolt the folding tip on and avoid the heavy hydraulic hoses and actuators.
