I think in the faction bank each member should have the option to put there own money in a personal safe that no other member can touch.
There would be no interest to gain. It’s for people that make millions and need somewhere to put there money until there city bank finishes. This could come at a price. Maybe a tiny percentage gets donated to the faction bank, or some money gets lost.
A lot of people would use this i feel as it would help protect against muggings.
Also this could come as an upgrade for the faction and the leader will have to pay to enable there members to be able to use it.
If you got kicked maybe there could be a link that could be in the factions side of the city to claim faction account money. Your money would not be able to be touched until you click the link and only you can claim it.
So you wouldn't have your money automatically sent to you if you were kicked.