Just read one of the descriptions of a battle in Pariah and it mentioned that they landed two of those Drop Cathedrals. Here's hoping.
The palatine almost makes me want to replay all the Saint Katherine's Aegis historical battles; the current Cannoness Superior started as a Dominion, quickly became a Dominion Superior, then a Palatine; that's when she discovered the shield of Saint Katherine beneath the altar of the Cathedral which was built in Honour. That discovery earned her the title of Cannoness.
When the rift tore away the occlusion separating the Desdaemona system from the larger Imperium, the return of Saint Katherine's Shield to Convent Sanctorum sees the Mission of Saint Katherine's Aegis upgraded to a full Preceptory. Originally, this was where the campaign was supposed to start.
But this Palatine... If I pick a common head, and set aside 4 copies of it, I could build the model in all 4 stages of her career.
As for Ynnari: I think Lelith will have something to do with Ynnari. They made fluff where Jain Zar was fighting at Yvraine's side, but they stopped short of allowing her to join Ynnari. We know Lelith is hanging with the Ynnari, and Vect doesn't mind because he gets the inside scoop.
Maybe when Lelith drops, there will be rules that allow her to retain her awesomeness even if she joins Ynnari? Or just a set of rules that she has when used as Ynnari that make it worthwhile? And maybe the same set of rules will be applied to JZ.