Had some possible ideas of some side scenes or at least how some of the legends would interact with each other.
First is Yveltal (goddess of death) and Ho-Oh (resurrection of the dead). I had put out a long time ago that Yveltal before she met the MC had tried multiple times to pleasure herself but before orgasm her power would kill her pleasure DEAD. So what would happen if Ho-Oh resurrection fire was used on Yveltal. I think it would bring many of those dead pleasure feelings back to life at once and they would become friends and do something sexy.
Second is Zygarde and Rayquaza since both took care of troublesome legends that they also become friends that help each other. They could even compare who had it hardest.
There could be some interaction between Ho-Oh, Yveltal and Xerneas with with Tapu Koko, Lele, Bulu and Fini since they all seem to relate to the cycle of life and death and in-between. Info is on the Guardian deities page of Bulbapedia for the Tapu.