I don't think there's a need for all these restrictions More or less because most people are smart and the logs can be viewed by everyone in the guild + of the restrictions placed by the leader who can control the Guild Bank settings, as all the other Guild Settings, if someone dares to abuse the feature and be selfish, that person would either be simply removed or his Guild will abandon him, seeing that he's unfit to be a leader.
I'd still like for gold, diamonds and runicite to be deposited, there could just be a game limit where people could only deposit and take appropriate amounts, like 100 dias and 1 mln. gold a day, let's say
And also there's no need for a ban on the leader, I personally think it will be a perfect experiment for guilds to see which leaders are selfish and abusive and let them crumble, as I said above.
Another great concept from WoW would be the action house, where players can put valued goods themselves and sell them for gold / diamonds.
This will create a sense of economy on the server and let players experiment and control their flow of gold / dias / goods + it will help players to more easily get the things they need, given all the insane amounts of gear and stuff required for the bigger gear tiers and legendaries.
And one more great feature from WoW would be the Token Exchanger, where people can trade off their tokens for ones they need for reasonable values
For example, FP / War tokens can be traded for 1:3 ratio for Coli / Guild tokens and 1:5 ratio for Expo / Soulmart tokens and vise versa. This can significantly help with the amounts needed for the newest batch of legendaries.