I got a good idea how about you could either pay him for extra spaces or too hold you're items. Or be able to build like a safe or vault to hold extra items
Why not have the adviser have an option to get rid of your quest and useless items for you? For example, he could sell quest items to the Antique Shop in Shilo, and give you some coins in exchange. As for the useless items, he would just low-alch them and give you any coins he obtained. or, you could just have him keep the profit for himself.
Good idea! I have another suggestion to add. Maybe the bank advisor could tell you the total G.E. market price of your whole bank? People are always bragging about having the most valuable bank, but this could give a realistic idea of how rich you really are.