Demetrios1453
Legend
What I would ideally want it to be and what I would realistically expect it to be are two quite different things.
Ideally want would be another setting book in the Eberron/Ravenloft mold, with a similar format to those two.
Realistically expect would be a hybrid adventure/setting book, sort of like Saltmarsh on steroids. Granted, the adventure itself will likely have maps and descriptions of Realmspace (perhaps various chapters of the adventure takes place on each of the worlds of Realmspace, ending with the illithid and beholder dominated outer planets as the finale) and the Rock of Bral (which was supposedly left to the DM's discretion on where it was, but it was often placed in Realmspace, in the Tears of Selune, in various products; it would likely be the first stop off Toril for this hypothetical adventure), which would be doing some of the setting portion's heavy lifting. The setting part of the book would describe the basic set-up (hopefully the crystal sphere and phlogistion system, although I'm not opposed for some ships like the githyanki and illithid to also be able to travel to an otherwise definitively separated Astral); how travel works; a description of a few other crystal spheres (maybe some, perhaps including Greyspace, in some detail, most others with a quick description); important races and factions; a few charts and tables for DMs to create their own crystal spheres, planets, and systems; example ships with stats like in Saltmarsh; a quick space combat guide; and of course a bestiary. Let's say it's around a 300 page book, so roughly 150 pages could be given to each of the adventure and settings section. Honestly, because there's no reason for a lengthy gazetteer (there really aren't that many crystal spheres that have been detailed, or need to be more than briefly detailed), the setting section doesn't have to be excessively huge like for other setting guides.
Ideally want would be another setting book in the Eberron/Ravenloft mold, with a similar format to those two.
Realistically expect would be a hybrid adventure/setting book, sort of like Saltmarsh on steroids. Granted, the adventure itself will likely have maps and descriptions of Realmspace (perhaps various chapters of the adventure takes place on each of the worlds of Realmspace, ending with the illithid and beholder dominated outer planets as the finale) and the Rock of Bral (which was supposedly left to the DM's discretion on where it was, but it was often placed in Realmspace, in the Tears of Selune, in various products; it would likely be the first stop off Toril for this hypothetical adventure), which would be doing some of the setting portion's heavy lifting. The setting part of the book would describe the basic set-up (hopefully the crystal sphere and phlogistion system, although I'm not opposed for some ships like the githyanki and illithid to also be able to travel to an otherwise definitively separated Astral); how travel works; a description of a few other crystal spheres (maybe some, perhaps including Greyspace, in some detail, most others with a quick description); important races and factions; a few charts and tables for DMs to create their own crystal spheres, planets, and systems; example ships with stats like in Saltmarsh; a quick space combat guide; and of course a bestiary. Let's say it's around a 300 page book, so roughly 150 pages could be given to each of the adventure and settings section. Honestly, because there's no reason for a lengthy gazetteer (there really aren't that many crystal spheres that have been detailed, or need to be more than briefly detailed), the setting section doesn't have to be excessively huge like for other setting guides.