I'm not sure if this has been suggested but here I go anyways.
Is it possible to have the amount of zeny in the Banker display in the control panel?
I like how we can view how much zeny we have per character but it doesn't give us an overall of how much zeny we have in total... this would save people from having to check in two steps (online and in-game). It would also hasten the process for those that have multiple accounts.