Cheat: Get Bathing Suits
Load a save file that's been beaten from the first Xenosaga game or Xenosaga Reloaded to unlock bathing suits for Kos-Mos and Ziggy.

Cheat: Skill Point Bonus
Loading the clear data from Xenosaga1, you can receive more skills points depending on character levels. The normal starting skill point is 600 + (level of character) times 30. So if your characters are lvl99 in Xenosaga1, you can get 3570Skill points.