[James O'Neill]

I recently read a post on "How much energy does an alternator use?". So I read some more online articles and found that some people have thought of running their alternator on their drive shaft. This doesn't seem more economical to me, since you will still loose engine power .
If the alternator creates engine drag and ultimately makes the car less efficient, how can you go around this without doing away with your alternator?
My thoughts:
Instead of running your alternator off the drive shaft with a belt, why don't you make the drive shaft the alternator? You could assemble the rotor around the drive shaft and fix the stator to the chassis.
Does this idea sound plausible? Or would it make the drive shaft too heavy and ultimately make the engine even lesser efficient?