You can never have too many guns. Likewise, you can never have too many bullets. If you're under 17, you can pilot the mecha of your choice. In fact, you're obligated to pilot it. This is where unlimited ammo comes in handy.
Naughty tentacles are a fact of life.
Deal with it. If the situation looks bad, simply jump to an eyecatch. That'll give you more time to think up an ingenious plot device to escape and save the day. Trained soldiers working for the villains still can't aim. However, if you're an inanimate piece of scenery, you're doomed.