To answer the title question, sorry, you can't add cards to your sideboard in Brawl
Though, are you willing to risk it all for a chance to get your hands on some of Hoenns most powerful Pokemon
If one of the targeted creature cards is an illegal target (for instance, because it has left your graveyard before Victimize resolves), you'll still sacrifice a creature and put the other card onto the battlefield
Since its the same Level as the Blue-Eyes White Dragon , you can simply Tribute a Blue-Eyes White Dragon from your hand or fieldor banish a Blue-Eyes White Dragon from your Graveyardto Summon a Blue-Eyes Chaos Dragon from your hand with Chaos Form
That makes colorless anthems, like It That Heralds the End (cast it with Volo for twice the boost), Forsaken Monument, and Ruins of Oran-Rief terrifying for anyone sitting across from you, and although they dont work on your disguised creatures thanks to that pesky ward, Muraganda Petroglyphs and Ruxa, Patient Professor can buff most of your face down creatures even further and stop blockers from interacting with them all that effectively