There are several key things that this will need to work.
First of all, the A-10 is a *masterpiece* of close air support, based on the hard earned knowledge and recommendations of the best CAS pilots who ever lived.
Therefore every aspect of it that is superior must be retained, with only “ordinary” elements improved.
For example, the “titanium bathtub” protecting the pilot is critical to protect the plane’s most important asset.
The total system redundancy has saved A-10s “shot to ****”, that would have killed any other aircraft. Amazing amounts of damage, yet the pilots were able to bring them home.
The powerful engines could be very conservative of fuel and run at low speed, allowing long time area coverage. But at high speed the A-10 really moves.
These are some huge advantages.
But there are several things that would strongly benefit the CAS.
Perhaps the most important would be to turn the aircraft into a command and control center for a ‘wing’ of drones flying with the aircraft. That is, imagine an A-10 with four drones “tagging along”, each of which could independently attack targets with different weapons. The pilot could order, say “Number 3, drop a bomb on this target I have just designated. Number 4 use suppressing fires on this target. Number 1 and 2, continue to tag along with me.”
A two seat version of the new CAS plane could have the back seater controlling the drones. Build a drone around the gun and have the control plane flying at standoff range working with a forward observer designating targets.
What I would like to see would be a two-seater manned aircraft controlling drones, with the manned aircraft staying out of range of anti-aircraft missiles. The back-seater would be the drone controller. He would wear a virtual reality helmet and have a high-speed link to the drones. He would be able to "see" everything at wide-field 4K resolution, enough that he would effectively "be" there. The drones, in turn, would be mass-produced and expendable.
The A-10 looks good now, but that is because of many years of expensive improvements.
I was on the original OT&E team at Nellis Range 63 when the first versions started flying. The first time the gun was fired, the pilot had to declare an IFE due to the canopy being so fouled as to have lost all forward visibility *and* an engine out due to gas ingestion.
It is hell on siting tanks. Moving, not so much.
IOW - the A-10 you see today is only remotely like the first production models.
Would a cheaper, lighter aircraft with a 20 or 30 MM chain gun in an underbody pod work? Bradley's brewed up T90s with a chain gun, so, yes, I believe they would.
For now & for the same dough, you could build/fly 5x or even 10x as many aircraft - literally swarming a target...
http://taskandpurpose.com/a-10-warthog-fighter-replacement/
BTW - the A-10 Thunderbolt costs just $11,000 an hour to fly. Oh, plus ammo.
Remember this competitor?