Kind of a weird choice, honestly. Clerics are already subclassed so
dang hard. And PS isn't especially cleric-heavy. Unless, I guess, you imagine every hardcore factioneer as a Cleric of Philosophy or something? That'd be...hmm...not great. I guess it could also be an Athar domain for dispeling magic or something.
I don't mind if they streamline a bit, cut down the number of planes/Factions. But I'm a bit worried we're going to loose some of the whimsy/weird due to balancing priorities. E.g. the Astral plane lost the switching mental stats for physical stats, I doubt spell keys/power keys are a thing, etc. All horribly unbalanced, but it added to both the character and the threat of different planes.
I seem to remember quite a lot of pages devoted to "this spell don't work like that" though.
When I run PS these days, I do it mostly without the individual planar alterations to various schools of magic. I do it 5e Ravenloft Style - I alter the vibe of the magic to suit the plane, but not the effects. I do like to keep spell keys or power keys as single-use magic items that you can use as an additional component to your spell to give it a bit of planar
oomph. Add a meditation mantra and some sand from a dead god to your
fireball on the Astral plane and there's a bit of psychic damage in it, too, for instance.
Weird local rules just don't really encourage exploration, but I like keeping them as a bit of spice to sprinkle in.
The more I think on it, I'm really wondering if they'll skimp on describing the Planes themselves, with a lot of referrals back to the DMG, and concentrate on Sigil, the Outlands, and the setting rules (which would include rules about the Planes in lieu of deep descriptions of them). This would make some howl of course, but it might be the better route to go. The original Planescape box only had 2 pages of description for each Outer Plane and 1 for each of the others, after all.
PS is not the Wheel and the Wheel is not PS. I'd hope they do PS as PS, with a quick overview of some of the outer planes (like the original boxed set had!) and keep the more detailed dive for a
Manual of the Planes next year or something. And you could probably even do a
Fiend Folio for demons and devils and assorted other critters where you dive into specific layers of the Abyss and the Nine Hells and such.
Maaaybe, though the Adventurers Guide for Planescape seems a more natural fit for player material.
Player Book: "Tarsheva's Big Book for Berks" (or the Planewalker's Handbook if you want to be boring)
Monster Book: "Xanxost's Menu" (Xanxosts's commentary on monsters would be absolutely worth sprinkling into a monster book)
Adventure: "Orc and Pie, but Philosophically" (an orc sits in a room with a pie and contemplates the nature of identity and the nature of utopia and what defines good and evil; the pie was made by a fallen celestial and each of the slices of the pie is actually a portal to an outer plane; you need to convince the orc nonviolently to let you eat the pie's slices so that you can visit the right planes to assemble a cadre of celestials, fiends, constructs, aberrations, fey, and other planar beings to convince the orc that it shouldn't be angry anymore; at the climax of the adventure the pie explodes because there's too much metaphor in it and the party has to fight Piesmodeus, who wants the orc to be angry.)
I actually think one big adventure is a lot less useful than a half-dozen short ones, so I kind of
hope they go more for the Radiant Citadel/Candlekeep Mysteries/Keys from the Golden Vault vibe than the
Light of Xaryxsis vibe. If they don't, maybe I do a few DM's Guild releases of my own....
