It's up to you.
It's like I told @marco1976 there's nothing wrong with it, but it does kind of limit who can download it. If it's a watchface that has similar watches like it out there, a lot of people may skip it opting for the easier to get watch.
That being said, if it's an awesome watch that uses the extra stuff well people will grab it.
Alternately, you could do two versions of the watch, one with the add ons and one without. If it's just for you, then do what you want