>Here is my plan. Get new queens for all my colonies.
After given time for all the old strain to have expired what will be my chance of getting a mixed off spring, "not knowing how many feral bees are in my area", from breeding new queens?
Meaning get feral survivor blood into the mix? The ferals tend to raise drones later and earlier than the domestic bees. Raising queens late, after the drones have been pushed out of your hives, will increase the chances of getting those feral genes. A quicker solution might be to buy virgin queens and let them mate in your location early before the domestic bees are rearing very many drones.