The idea is based around the training Krillen and Gohan do on the ship to Namek.

The battle allows you to fight other characters but set both fighters to the same level, the characters stats would be edited to fit their set level, this allows you to test your new signatures/ultimates on a some-what equal opponent, this could also help new players by giving them a taste of being a higher level while also explaining how to battle. Although all battle will not give you xp and are merely for testing and fun. It could also help with balancing races and characters.