I'd really like to see LeVar Burton's La Forge return for this series to flesh out the cast, possibly as a Captain helping out Picard with whatever's going on.
Also would like to see Gates McFadden as Crusher, obviously, and somehow get Brent Spiner.. He can play a Soong of some sort. Maybe somehow get Ro Laren back? What's ole Michelle Forbes up to? In regards to Q, and given that de Lancie has aged as well, he could still antagonize Picard, even "appearing older" to remind Picard of his mortality while Q can just do whatever he wants.
Would be down for any cameos from the DS9 crew, especially Sisko, Kira, Miles, Garek, Martok, and well, just get Jeffrey Combs on the damn show. Would like to see a stand off between Kira and Ro.
Don't like that it's on All Access, but would watch.