Bonus level:

After the Pirate missions are complete, you will arrive at the Canyan Ends in the middle of a island-like area. it is extremely difficult, and the only way to finish may be to be Dishonorable (enable the "Invulnerable", "No heat", and "Unlimited ammo" options). You will face pirates and People on your own team on the Fed.Suns Missions.
Easy kills:

If you are playing in Instant Action mode, choose the water terrain (the Road to?). There is a bridge not far from the starting location. Go to the bridge and hide under it. The enemy Mech AI will have trouble understanding this tactic. They will almost never come into the water to get you. They will often sit on bridge while you peek out from below and blow them to pieces. If done correctly, you can take out ten to fifteen waves (thirty to fourty Mechs) before you take significant damage. Since you are in the water most of the time, remember to take lots of lasers. they work well in the water and heat should not be a problem.