1. Launch a mission in the "Combat Simulation" room with whatever mech you want.
2. Abort the mission after you launch.
3. Quit Ghost Bear's Legacy.
4. Log on your campaign mission briefing.
5 Whatever mech you used in the Combat Sim, should appear as the mech you will use in the campaign mission!*
*note: you can't do this trick on missions that let you change your mech. Or the underwater mission.

