No, Don't waste your time making an fps that will just fail in flash. there's too many fps'es, try making something original, not just adding another game to the fps category where it will get lost.
You could add an money generator along with the bank. So that while you are waiting for the bank, the money generator creates money for you and you can upgrade it. But you have to constantly recharge it which costs money. The more upgrades for the money generator, the less you have to recharge and more money you get.
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