Didn't someone point out earlier that it was likely that the scum are Valmese? If Tiki's worshipped in Valm, wouldn't that make her an antagonistic character? Could the announcer be scum?
Valm kind of goes through a civil war during the course of the game. Although many of the Valmese that you meet are antagonists, there are members of a "Resistance" that join Chrom and the Shepherds and would definitely be considered good guys. Tiki's one of them, another is Say'ri. Yen'fay is kind of on the fence; he's Say'ri's brother and a boss that you fight, but his actual feelings and motivations are more aligned with the Shepherds and he's basically only fighting because he was blackmailed.
Technically, you can recruit him as a PC in a special, extra level right before endgame... but you can also recruit Walhart and Aversa (who in the actual storyline are basically 100% baddies through and through), and Gangrel (who I think is most fitting as an OMT type, but I could also seem him scum-aligned).