Combine the Choice and Multiple Choice Fields

This is always an issue for me. I start with a Choice field and then I realize it should have been a Multiple Choice field, or the reverse. So thinking about it a bit, why not just have a Choice Field that can be set as single choice or multiple choice, say with a checkbox. This option could be turned on and off. And when turned off the suer would be given the choice to create indiviual records of all the multiple choice records. You folks figure it out, but somehow the ability to convert would be very helpful.