If you capture an enemy Wanzer at the end of a battle, keep it. This way, if you lose a Wanzer in your next battle, you have a spare Wanzer to replace it. Besides, you do not have to replace any destroyed parts on a captured Wanzer; they are automatically repaired for you. Just make sure that you add some weapons to it, because your only attack on a captured Wanzer is the HADRBLOW, which is the weakest.