Eternatus being from space makes it sound like she's going to be rivals with Rayquaza as well as Zygarde, I can see ehr being friends with Deoxys, maybe she could even translate for her!
The MC using Eternatus as a giant bed is a pretty cute image... hell he could bone some of his other girls while laying on her tummy!
It did occur to me that I can use Dynamax to help the MC fuck her too!