Well, yes they do.Well no, they don't. Since Vietnam, the Marines have been demanding their own air force but they don't need their own air force apart perhaps from lifting troops off their carriers--hence the MV-22 which is a mission enabling technology as it has such extended range.
The navy and the airforce are not nearly as good at CAS for the marines as the marines are. That is why the marines do have their own "air force" and always will.
Marine pilots train for CAS, navy pilots know how to do CAS. That is a big difference. And marines on the ground transistioning phase lines are not going to trust a non-marine with critical fires. It is what marine aviators do. As part of the deal, they float VMFAs as part of CVN Wings. I guess you missed the memo on that one.
In any event, as I have stated before, the MV-22 has legs but not lift. This is a large problem for the marines. A BLT needs to move some large heavy stuff fast, especially in the fires function. This is done by 53s. MV-22 can not do it. If you take away the 53s, the lighting part of a BLT landing (otherwise known as "violence of action") is not there. They can not transition past the first phase line without organic fires. The faster this kit makes the beach the faster the BLT advances. MV-22 does not do it. The AV-8s currently help fill the fires transition gap until heavier items make the fight. Without the AV-8 CAS (or soon to be F-35) CAS role, that leaves the marines hanging with sustained fires to support the advance or manuever functions. The reason there is a V/STOL requirement for CAS is that the marines use AV-8 from FARPs to add depth to the battle space. FARPs give them much faster CAS cycles than feet wet/feet dry does. F-35 will fill that role with AV-8 going to the boneyard.
You really do not understand so much how an expeditionary landing is conducted and the requirements to support it. It is a very complex animal and V/STOL CAS has a key part, as does feet wet CAS from primary role fast movers like VMFA. Dynamic phase line CAS is NOT what you have watched on TV for the last 10 years. That is Strike.
Two different animals. If anyone executes operational art with full understanding it is the marines. They know what they need to do, and they know what they need to do it. They know they need the F-35. It was not forced on them, and what it brings them is huge.
On another note, the AF CAS guys are more akin to Strike and rolling fires. They are not nearly as dynamic as the marine flyers. The main reason is that the AF trains to support the army. And the army treats combat aviation as a maneuver element. The navy and marines do not. It is a fundamental differnce in employment philosophy that in simple terms causes the AF to stay Army focused. They foray to some degree into the maritime, but not as experts. The other part to this is the the marines have integral to the C2 construct the organizations to fully integrate marine CAS into the marine fight. This is another part of the system that is critical. Marines practice this all the time. The AF and USN hardly ever go in for full marine support, and when they do so they use standard joint methodology, not the polished familiarity that is found within the marines themselves.
You are really trying to bin things into one size fits all arguments, and it doesn't work. The complexity of the topic prevents it.
I as much as many would love to see the A-10 fly on with an upgrade package, or even update build. I would also love to see the same for F-22. But neither of these are going to be primary support options for USMC operations, just like VFAs aren't. It ain't what we pay them to do.
For the record, as you know, I am not a marine either.
You can't have it all. And F-35 is a good answer. Really good. There is no match for it, and won't be for a long time. It really is that far ahead.