The AMA (motorcycle racing folks in years gone bye) tried the same thing with "National Numbers" in the early fifties. It mostly caused hard feelings, especially with those who had held a certain number for years and didn't want to change to a different one every year. Just think about how much repainting will be required (unless you switch to washable poster paint), and how much confusion about who is number "x". Since I don't have a number, I don't have a dog in the fight.