Sadly we are so risk adverse and programs move like molasses. Their are newer airfoils ( high lift, low drag, low pitching moment is not out of the question tailored for this aircraft specifically, the current airfoil IMMIC has a G-d awful pitching moment ) , wingtips (1/4 ellipse for example ) DogTooths, VG’s etc etc that could add some performance on the top and bottom end, however they will not be designed to be incorporated on this buy, it is a blessing to get the buy alone. Sadly this would be the time to take it to the next level, but the days of things moving fast, aka P-51 designed and flying in 100 days, or Lockheed getting-er-done fast in the dark world won’t be applied here...
You obviously have some aero design background, as do I. A lot of the basic A-10 design was already optimized - straight wing, engine position, gattling. So you really don’t need a new airplane design, just a components upgrade. The newer versions of that engine for example put out a lot more trust.
The physics of the F35 are simply not optimized for low cost CAS (a low aspect ratio makes no sense). And it isn’t like we are having A10s shot out of the air now, even with the slower airspeed.