RS Gold player's idea of this usurpation of Gielinor, posted on the Runelabs and seems a great idea. So here it is suggested by Soni.
We see a massively integrated system of banks all throughout Gielinor. Everyone uses them, from all the way in the desert and Morytania to the Elves and Prifddinas. Because players can deposit and withdraw from their account at any of them, it can be assumed that they each have a large collection of items. Chances are, a quest concerning the bank system would not be focused on having access to all the player's banks, doing so is more like World Event level of play.
The quest begins by talking with King Roald in the Varrock Palace. He appears to be in distress and when asked if something is going on, he makes some cheesy speech about being able to trust the player or something...and tells the player about the Royal treasure being on hold. He reassures player that he is a stock of gold in the vaults to pay for expenses, but if the main account isn't accessible soon it will dry up.
Roald tasks you with checking the other kingdoms to see if they could offer temporary assistance if needed. It's a simple running and talking to people, who would each describe that their Kingdoms cannot assist becausethey could be facing the same difficulties. The Dwarves are likely to be most angry about all their vast amounts of money being kept from them. Once done, the player returns to Roald to describe the situation.
King Roald asks you to seek Barb, the Treasury Adviser of Misthalin, since she knows the most about the Bank system. Meanwhile, he will be organizing a meeting of the leaders of the various kingdoms to devise a plan to take back their resources.
Barb would most likely have a home in Lumbridge. Despite her knowledge of banking, however, she amazingly doesn't know who is in charge of the bank system as a whole. Fortunately, she recalls thet Trader Stan in Port Sarim has often bragged about his conncetions to bank leadership.
Getting any information from Trader Stan would require use of the Ring of Charos, otherwise it will be futile conversation. Even with it, he doesn't give a straight answer. All he says is he stays in Sarim because it's close to the operations. Perhaps other clues in how he talks, but point is the next step is to check on Entrana.
To be continued... More information about this suggestion would be found in Runelabs.