The releases where the box was the diorama- the Hoth Set, Endor set, and Han/Mynock set (I'm sure there were others, but I think those were the only ones I had) were all really nice, but just took up too much room (ironically). The Endor set especially- awesome presentation, but a heckin' space eater. Plus, as an OOB collector, I want to pose my pretty little plastic people in ways that won't warp them from the bubble. I really do think that some larger Black series dioramas could work- at the very least, some sort of segmented thing like the Tantive IV or Death Star Walls. Something you could as a display, but also photograph well. An Endor bunker would be cool as well, or if they'd given us the Duel of the Fates set with one of the long platform pieces. Pretty much all of these and more can be bought 3D printed from places like Etsy, but they're pricey little suckers. Worth it, most of the time, but still.
It also surprises me we never got any sort of War Room holotable or anything. Especially once they started releasing the Holocomm Collection (may she rest in peace). I know they included the pucks, and again, there's some cool customs you can get that give the impression of a full-sized hologram. But that would've been such a cool way to display the Palpatine Holocomm figure we never got. Something like the sets they made back in the day- the Jedi Council set and the Geonosis War Room set- could be really cool, even if it would have to be bought in sections like it was before. The former would have to be massive, but a nice little diorama of the latter with all the Separatist members around it could be awesome.
Good choices all around, doc! I agree that a Palpy's Pals set would be awesome- Sly Moore and Mas Amedda (with removable tongue, of course). Do the same with other factions- Senate with Padme, Mon, Bail, other aliens. Separatists with San Hill, Wat Tambor, Rune Haako. And of course a Podracer pack or 2; ones they don't think could sell on their own, but might in a pack. Some non-droid/non-clone Prequel army builders would be nice as well- Naboo guards seem like an easy enough give, and if it leads to Panaka and/or Typho, all the better. Sio Bibble and Ric Ollie would unironically be welcome, I think. They're basically nothing characters, but so silly and so earnest that they wind up being charming. Say what you will about the prequels, but they really are gold mines in terms of cool character designs.