When you hit an eb you are technically using all your soldiers. What happens is some die and you just repeat. So the game already sends "all". You just don't see it. Hope this helps you understand why the unload all button wouldn't work
Let's go one step further, a switch you could turn on in your options so you only have to press the app logo on your screen. Then it automatically unloads, builds building for you, and buys pots. After you do this 100 times, it hits the battle list for you. After 1 million presses it writes a forum post about your retirement and resets. SUPPORT!
Well if your really rich just hire someone to grow for you, then take all the credit at the end. Or just "donate "a few million to ATA and I'm sure they'll "set you up."