To answer the initial question, yes it can be done. I was hired by the Kansas ANG back in 1995 to fly B-1s. I was commisioned through AMS in '96. I went through all the training and flew for about 3 years before the AF reorganized and pulled the Bones out and left the unit with KC-135Rs (no navigators) and some really cool desk jobs (they really were, no sh!t.) However, I hadn't hit my first flying gate and still enjoyed flying. I transitioned from the Guard to Active Duty.
Many guys who have worked under both systems generally joined the Guard to get away from some aspect of the Active Duty lifestyle they didn't like. In my wing, I think only about 4-5 guys switched back to Active Duty.
The other consideration is active duty manpower requirements. When I made the jump in 2002, the war had just kicked off and they were trying to get aviators any way they could - some guys were even being brought back after separating from the AF. Currently, the AF is trying to reduce numbers, so it might be harder to transition to Active Duty right now. Just like with uniforms in the Air Force, if you wait a year, that will probably change.
There are other options to consider. I think there used to be some opportunities for Guard guys to take a 2-3 year assignment working in/with the active duty that were designed to provide "career broadening" Current guard guys can probably provide more info on that, but there are probably options there as well.