Mmm, maybe there is a mod where there are actual coins that can be made from gold using a stamp/press of some kind? It would give Gold a lot more value in the game rather than just being used to make things look pretty... It would also enable banks to be created alot easier! I suppose it would make banks more easy to break into, but thats all part of the fun isnt it
But for the problem of bank security, maybe just have a rather large amount of bedrock vaults, say, 3 by 4 in size, and you need to apply on the forum to own/rent one. Once you have succesfully applied, you get a mod to create a /vault or something for you in your vault so you and only you can move freely in and out? I have seen something like that done on another server, and it worked very well actually!
I definately agree though that money needs to play a more active role in the server!