They could always make it so that the pet skills you have to assign to your hotbar change depending on whether you have Eos or Selene out, with Eos having the same AoE regen and incoming healing boost, and Selene having the old skill speed buff but not really sure about the second skill.

Since Selene is utility focused maybe she can extend the duration of chain stratagem, or offer something similar to a chargeable swiftcast where the next spell is instant to make SCH able to mass rez easier like RDM can. They could also make the pet casts instant like summoner and have separate charges so that pet switching according to what's happening in the fight will be something high end scholars will be doing on the regular.