Regarding reality, nobody in no airplane is going to be performing CAS inside an S300 or S400 threat ring. So that argument is irrelevant. Now, lets assume, for whatever reason, your intrepid USMC CAS asset is forced down into the weeds. Exactly what weapon do you expect him to employ? Dumb bombs? Guess again. 20mm against armor? Pointless. And if you plan on designated his laser guided stuff, that's fine, but have you actually tried that? If so, you know he's not going to be in the weeds when he releases them. And he will be miles away from you when the bombs come of his airplane.
This is going to trigger you again, but the more you say the more you prove my original contention. The strongest advocates of aircraft like the A-10 on threads like this are people who have little or no current knowledge about what they are talking about.
With some luck and some inspired leadership, the Army and the Marine Corps will have our own unmanned platforms delivering precision and scaled effects when and where we need it.
Now if and when you do find yourself "down in the weeds", cannon is a good call, since it is excellent against troops, particularly against troops in light cover and best of all it is linear and can be employed very close to us with little danger. Dumb bombs also work fine, as long as you are clear where the target is and you have had enough range time to actually hit things. You left out rockets - another nice, linear weapon with excellent effects. Just remember to eject over us if you can and we'll provide lunch when we come get you.
P.S., when you are computing my service time, add the 3 1/2 years between my first four years and the next 23 years: I had to heal up a while before I could resume service. Also add 14 years as a Technologist for a certain battle lab. Other than that, you are spot on.
Semper Fi, Snowflake 6 Actual