I always thought it included smileys as images. That's the message I always used to get when I tried quoting a post with 4 smileys, and adding a smiley of my own.
it's a good idea but lets look at the roots of this problem - people are saving items because bank cant hold all the cash!
Just increase bank level and let people save lets say $50k or more and problem with too many items in inventory will be solved as only a few people will save items in backpack and most will sell items for cash (as in all normal games they do). Its not so hard to sell 1 and if you are lucky 2 items a day and see your $$$ amount in bank increase