So, a week or so ago, Sym (with help from Ratchet) came up with an idea focusing on the bank.
We could have two banks: A bank just like the one we have now, for depositing, withdrawing, and transferring at will. Then, we could have a tu-locked bank. With this bank, you set a tu goal that you want to reach. Once you do so, you may deposit tu in this bank at will, but cannot withdraw any tu until you hit the set goal.
This second bank would be great for impulse buyers who really need to save tu. With this, we could save up tu without spending it, but still have our normal bank accounts to transfer, deposit, and withdraw as we like. We could put some in here and there while still having tu to work with.