What the others didn't really point out is that the F-35 is definitely capable of what the A-10 does and more. It is faster, brings a drone-like attack platform, and can engage from much higher altitudes.
And this is coming from someone (see my other comments) that doesn't particularly care for the JSF/F-35. The A-10 needs to go away, and the F-35 will be a more than capable replacement for it.
Now, the other F-35 roles...
Flying at higher altitude is also not necessarily safer - it puts you out of reach of MANPADS, but in clear view of larger SAMs. Evasive flying generally involves nap-of-the-earth flying, which hides from larger SAMs in radar cover and provides MANPADS and AA artillery with short engagement times. The A-10 is also built heavy and robust enough that MANPADS often aren't enough to bring it down - only vehicle-mounted or static air defense systems have big enough warheads.
If anything, the problem with the A-10 is that it's overbuilt. Its cannon is built to take down tanks in an era when air-carried cannons probably can't get through modern tank armor, and is heavier than is strictly necessary for an anti-infantry role. The air force is looking at much lighter planes like the A-29 and AT-6B for low-threat environments, but could perhaps field a plane with similar loiter-time and survivability characteristics to the A-10 with less weight wasted on that ridiculous cannon.
And higher altitudes are strictly safer, even against SAMs. If you’re at virtually any altitude above terrain masking you’re in sight of them. Altitude gives you extra time to react plus requires the missile to burn more fuel reaching you in the first place, shortening its range and increasing the tools you have available to defeat it.
For the tanks, the A-10 carries the AGM-65 Maverick with 136 kg (300 lb) of explosives.
Upgrading the gun would be useful. We can now make even the 12.7 mm ammunition have guidance, so 30 mm should be easy. We could compensate for the density reduction by upgrading to something like the 37 mm used by the MiG-17. Guidance would allow targeting the most vulnerable parts of a tank. The toughest modern tank still relies on vulnerable sensors. One could also just pound the same spot many times, chipping out a hole. Reactive armor is nothing if you can get a second shot in the same location.
Sandia National Laboratories did something similar, but with a non-standard rifle and using a laser target designator. Russia is attempting to do something similar.
Of course that could all be a lie to throw adversaries off the scent, but the trouble with trying to keep a bullet top-secret is the moment you use it, the enemy has as many as they want to study...
Many years ago I saw a concept of a guided machine gun bullet in a "scientific" magazine; the concept involved steering by a mechanism that moved a lump of mass within the bullet around.
A B-52 could loiter all day long and carry more bombs than a squadron. In fact, the USAF brags about B-1/52’s doing CAS.
So whats the unique need for a fighter that costs as much to operate as a B-52.
>So whats the unique need for a fighter that costs as much to operate as a B-52.
Achieving air superiority, alongside our limited numbers of F-22s.
That said, it's also one of the best dogfighters in the world in case it ever comes to that, but that kind of combat will be deliberately rare.
Against countries that can punch back?
There is also a VTOL variant of the F-35.
I generally agree with your comment though, the A10 doesn't work well enough without air superiority and is comically overbuilt for operating with air superiority. The platform is just... old. It needs to be retired, needs have changed but unfortunately the existing menu of aircraft can't really fill all the niche corners of the CAS role as well as the A10 can.
Sadly, if only this were true. The gun's published accuracy numbers have 80% of rounds landing within a ~40ft diameter circle at 4,000ft engagement distance. When the gun is fired—typically in one-second bursts—the nose of the plane lifts noticeably by several degrees and so the gun is always employed in a strafing run: you aim a bit below the target, pull the trigger, and let the target pipper rise up across the target. To make matters even worse, its targeting system is the Mk-1 Human Eyeball.
Even in the best possible scenario, you're firing the gun in a high-angle strafe (30º of dive) from 1.2–0.8nm, where you're talking about something closer to a 60ft circle of death that traverses 50ft across the ground while narrowing to 40ft in diameter. Not to mention the 20% of bullets that fall outside this area.
All this is to say that if you fire the Warthog's gun at a target across the block from a school, there's going to be a very serious press conference happening back at home the next day.
You'll see a lot of videos online where the gun seems to perform better than this, but it's always at static target practice ranges where the pilot is flying extremely low and has the benefit of doing multiple practice runs. In real combat footage, the plane is much farther out and the spread is correspondingly much wider. This video does a pretty good job: https://www.youtube.com/watch?v=NvIJvPj_pjE
I think the point was that a smaller gun would do. A Toyota pickup doesn't need an anti-tank round. Something more like what the Super Tucano carries would suffice.
That said, antitank weapons are good enough that well trained and equipped infantry should basically laugh off a BMP (or any other AFV) in most situations and there's always bombs and missiles.
[qoute]The Serbs quickly learned that opening fire on Hogs with AAA or SAMs made them both obvious and high-priority targets. Serb air defenses attempted to plan their missile and AAA shots to maximize the chances of hitting an A-10 while minimizing their own risks. The “SAM bush” was one such tactic. The Serbs would first fire AAA to make the A-10 jink. When they thought they had the pilot’s attention focused, they launched one or more SAMs in the hopes of scoring a hit. The SAM-bush had zero success, and often the A-10s made the Serbs regret they tried it.[/quote]
[quote]On average, Serb antiaircraft missiles and AAA engaged each 40th EOG pilot about six times—several pilots were shot at much more often... One A-10 AFAC point of pride was that, even though we often took aimed fire in daylight, none of the hundreds of strikers whose attacks we controlled were ever hit...[/quote]
from A10s Over Kosovo