The quirk that All Might possesses is called All For One. It is a quirk that can be passed from one person to another and it gains more power each time it is passed. All Might gave Deku (Izuku) a sliver of his power by making him eat one of his hairs. If this is how it can be passed than isn't possible for that quirk to be passed to a multitude of people? Say, an army, for example.
All Might himself said:
After I've given Izuku my hair/DNA, I've gotten a lot weaker
So it would either be a one time thing, or every new user would weaken him substantially so it would still be a small number, and probably of lesser effect.