Combining Gringotts and money on hand.

A simple idea to combine the two of them so you would not have to withdraw and deposit for everything to be bought and for when you gain more money on the site. So if you have 1000 Galleons on WoP it would show that in the dropdown menu and you would be able to buy everywhere with it. So if you've fainted you can purchase the medicine right away without waiting an hour or depending on having 200 on your hand that you could potentially drop anyway.

Almost everyone has their money in the bank for daily interests anyway, so I see no reason that this cannot become ideal for users and an implemented feature.