Mail 10k cr to 20 alts, get 20 times the interest.

Any sort of free limitless cr that doesn't require effort is out of the question.

Do you know why banks do what they do in real life? In the simplest terms, banks pay, using interest, to use the money you deposit.

There is no reason for OOO to establish a bank.

Make bank accounts non-withdrawable, but can be used for purchases. You drop in 20k, and earn interest on it, but that 20k can't be sent to another account.

Kinda like a guild treasury for you.

EDIT: Perhaps add that purchases made with an interest gaining account have certain percentage fees, based on the interest percentage chosen? So you can have lil' nest eggs, which gain nothing, but also don't cost anything. Opening and closing accounts also costs? I've no idea.

My suggestion is basically a guild treasury for an individual player, which gains interest. Yes, you can purchase items and send them away, so it is still exploitable. My idea only fixed the "send free crowns to alts".

So, here's another idea. Items bought using bank account attach to the bank account, which are locked to that player; which can only be sold to vendors. In effect, you have two inventories. One of which gains money, the other doesn't. Depositing crowns into the account comes with a certain fee, depending on interest of the account and the size of the deposit (so, dropping in 20k, doesn't actually drop the 20k, say, 19k instead).

As for what Oatmonster said, obviously you would. There's no way to gain interest without actually being able to make use of it (that's kind of the point; it's not like a real bank will accept your money, but never give the interest it gains to you).

Gain 20 times the interest.
That's 20 times a fixed interest. For low amount, that'll be quite small. At some point, interest on one super account will outweigh multiple accounts gaining little interest (I'm too lazy to work out any math). So multiple accounts with small interest isn't "always" better than one account with high interest. Again, as I said depositing does come with a fee. You'd be weighing the cost of dropping crowns against how much you can gain from interest.

Plus, interest wouldn't give A LOT of crowns in a short period of time. So, unless you plan on making 20 alts, depositing a lot of crowns, then leaving them alone for months, it's a terribly long process for the sake of a few extra crowns; which you can just get by doing a couple of runs.

Banks strength lay with inactive players. Active ones get little out of it.

PS: If you mention "I can buy items with interest gained, then sell them; so it's exploitable". That's not really an exploit. If it gains money, the money can be spent. There's no possible fix for that. Real banks work quite well, so why would a virtual one fail so badly? (don't answer that, I can see the problems with it).