It depends what kind of ground targets you want to engage. If you are in a full scale conflict and dealing with large number of land forces, with organized and mobile air defense, you will need more sophisticated aircraft to provide strike missions. But if you are fighting insurgents than pretty much anythin will do that can fly and fire something.
Personaly, I think that whole system of warfare needs to be re-designed since warfare itself has changed. Need for highly integrated platforms is smaller nowdays than it was before. It's kind of funny with the economy calculations, chasing 3000$ worth of pickup van with 6 insurgents armed with 2000$ worth of weapons (ak47,rpg's), creates a need for a weapon system that costs arround 5000$. Using A-10, (it is effective, no doubt about that) for such targets is too expensive. So the best way to eliminate that truck,by my humble opinion, would be an turbo prop UCAV armed with 50 cal machine gun, since it is cost effective or airborne javelin missles if things get more serious. That 50 cal machine gun would need a superior optics so that can fire it's rounds in a populated areas and avoid unwanted deaths among civilians.
Something like OV-10 bronco with 50.cal machine gun turret and few javelin missles, looks fine to me.