[Matrixbeast]

Yamato only said that line once an episode, and sometimes it wasn't even him.
Lucky drops "YUUSHA LUCKY!" once every 5 minutes.
We had 2 "Don't mess with this planet!"in Zyuohger by episode 2. It was basically part of their role call.
We've had over 8 Yuusha Lucky's already.
Trust me. It's going to get old. Very old.

Considering finding other members, here:

Tenbin Gold and Hebitsukai Silver were thieves, right? Have them partaking in thievery and Lucky wanting to apprehend them. The rest of the team basically says "No, other Kyurangers are more important than a couple of robbers," but Lucky goes down anyway because fireball red and confronts them. Have Balance recognize him, and try to convince him in helping steal the jewel with a fake Robin Hood act, and proceed as normal.
Of course, there'd have to be a series off coincidences (Why were they in X system, at that specific planet, to find those two), but it would be a hell of a lot better than literally throwing a dart through a projector, going to that planet, and just randomly bumping into them and immediately declaring them as the next Kyurangers.