Well, it's your bike at the end of the day, but that argument doesn't persuade me at all. I prefer to go for the most appropriate approach to each problem. For an alternator which can be controlled by a simple and robust piece of electronics that is cheap and easy to buy, building your own microcontroller makes no sense. For some things, a microcontroller is a sensible solution. That doesn't mean that just because you have one on your bike, you have to use it for everything.