Lets say you like dicing (*cough* Habaneros) you could put some of your meebles (put some in every day or something) to save and then when you get really poor from dicing alot you have extra meebles you can take out in that bank.
Or maybe you could exercise some self-restraint, refrain from dicing, and save meebles in your balance? If you're a dice addict, simply putting meebles in a bank account isn't going to do too much--you'll just end up withdrawing them anyways.
Another reason why you could use it is if you did not own a town you could use the bank for meebles (if you owned a town you could use the town bank for meebles.)
I'm not exactly sure what you mean here. Do you mean the bank would give meebles to players, or do you mean its use would be as a storage facility for meebles?
One big reason is no one could take your meebles, as in a town a co-mayor could take withdraw the money from the town bank (some towns have fallen for that reason :/.)
Co-mayors are forbidden to withdraw money from the town bank if the withdrawal would leave the town less than 7 days away from falling, so this is a non-issue.
I do not see any point to adding this plugin, particularly when other aspects of the server go neglected (*cough* CTF *cough* parkour *cough* creative). It would waste valuable development time that otherwise would be going to those areas.