This is quite cool but you might have to start looking in that direction of charging something for withdrawals no matter how little because eventually when the volume starts increasing, the cost might become too significant to bear and the moment you want to start aggregating withdrawals in other to minimize costs, be ready for people suspecting some foul play. Another reason why you should consider that is because, when I know I would be charge for every withdrawals made, I tend to minimize the frequency of doing it and that to a large extent would give your own platform the opportunity to have some liquidity in the time being which would have been withdrawn should there be zero charges on such.