Let me say the side bar about Yuffie summoning him with materia has me cackling so hard, I love it.

Aerith would be down to do that, she can zap whatever needs zapping even tho he’s like King Lightning Bender so he can totally out zap her any day. And he doesn’t even require an extensive twirl dance to cast

As for Eustace, they can bond over mutual annoyance regarding moogles and their ilk. They just simply go too far kupo.