I actually discovered this too, I apologize for not coming here sooner. Thanks for the tip @dck. On my first attempt I tried replacing the actual unit with Ritz, knowing Ritz functions as a Viera, I tried to change Marche's race to Viera. That didn't work at all since it just loaded the default Marche (sort of like when you set an empty slot to appear in a battle, it's a horrible level 1 soldier.) And I couldn't even get past the introductory battle where you first meet Montblanc.