The A-10 does one job, and there are several other aircraft that do different jobs.
The A-10 only does "one job" because that's all it's been allowed to do. However it has on occasion gone outside the box with devastating results against a variety of primary ground targets not in a CAS role, and it could also be used against maritime targets in the same way. The A-10 has demonstrated devastating anti-aircraft ability as well, with at least one known air-to-air kill. This is an area that could easily be expanded: no known aircraft can survive the A-10's gun. It is the most powerful dogfight cannon ever put in the air.
That's the key: very few things used in war or on a battlefield could resist that gun. The A-10 is likely to be a formidable platform if it was allowed to do more than CAS. Let it hit buildings, vehicles, ships and boats, and aircraft. All the A-10 needs is freedom to shoot anything that needs to be engaged.