[Sky Shark]

From how BOA likes to market things Gaim or Fourze would probably work best both have pretty plentiful toy lines and both could be down scaled to BOA quality quite easily. For lockseeds they could just use modified Sound Lockseeds or just modified the backs and load all sounds into the belt. For Fourze they could downscale the belt and just remove the led display. Gaim also has the whole arms change so BOA would have a field day on that for the playability factor like zord builder.

Hell with some clever modifications they could probably just flat out use Gaim wholesale while removing the death elements and Fourze just feels like a power rangers series(a good one) in a way to me.