I know its not possible for AI to work without a control tower, but I'm just wondering if anyone has found a way around this problem?

Use AFCAD and add a control tower.

You will also need to add tower & ground freq. If it doesn't have parking spots, you'll need to add those also. I've noticed that some of the uncontrolled airports do have taxiways & parking spots already there. But after all that you will need to add traffic to that airport.John

Thanks for the info guys. I know that I can add a tower, but that would make it really unrealistic. Has anyone found any way of doing it without a tower?

Just turn off your ATC, adding a Control Tower does not change the visual scenery.