Perth Falcons wearing East Perth Royal jumpersThe mascot can be anything really, I just said Falcon because it's unique to WA as there's no original VFL or SANFl team with a Falcon mascot (same argument for why I think South Adelaide Panthers would be the best SA3 team).
The important thing is that the club should be called "Perth" - so a tripple merger of Perth, West and East or just go with a brand new franchise.
Perfect 3-way merger