When cycles end your character list will be flooded with characters most people won’t use. Would be nice with an option to move these old characters to offline mode.
Items from the bank you want to keep must be in the characters personal inventory.
Materials should be no problem to move.
Many people who play online would transfer to offline after seeing how the servers perform, this would also help server stability. I’d say it’s a great contender for the priority list.
Right now every single dev is working on fixing the server issue. Implementing this would require pulling devs from fixing the servers to create a system that won’t really be necessary if the servers are fixed in the first place. So, no, not a great contender for priority.