I am not a programmer or painter, but I am impressed by all of the talent involved with this hobby. Would it be possible to write a program, maybe using an XML gauge, that would monitor the amount of time an aircraft is flown and over time weather the paint or make it look dirty?

Yes.Head over to www.flightfactory-simulations.com and check out their Van's RV-7. I don't have it, but the reviews all talk about how you need to "wash" the plane periodically to get rid of the virtual "gunk" that accumulates. Apparently, they've worked out a way to change the textures as you accumulate flight time.Yoda