there is no way to harm players in kaw other than to take their gold or deny them their ability to make gold. i don't see a problem with a steep fee on keeping your gold 100% safe.
It would make hoarding gold with no consequence too easy. No one could get your gold, and you could just pile it up. Bronze bars and potions are like a bank, in that you can use them to bank your money safely away from raiders. But to even the score, once you sell the potions or bronze bars to get your money, you lose 25% of the money that you spent. So a bank is impractical at the moment, but maybe the devs can work something out. Until then, no.
you do realize it is possible to keep someone pinned to the point where they can only make money on ebs if they obsessively attack it every ten minutes and/or make sure to be on for items, right? and you can take all of the bonus gold at they end of the eb as long as they aren't on to bank it.