Even if you used weightless atoms to fill your balloon, the lift is only the weight of the air it displaces. So you don't really get much better since hydrogen already weighs so little.

Air is about 30 grams per mole and hydrogen is two grams per mole. So going entirely weightless you could go from 28 grams of lift per mole to 30 grams of lift per mole, a 7% increase.