I think they mentioned that parts of Sigil involve pocket dimensions. But whether they do or not, they should use that idea. You should be able to go into a normal-seeming house and it's a mansion with weird gravity inside.It is odd sigil is very material plane.... It should be a lot more weird and different. Good points above!
And really emphasize the idea of pocket dimensions in Sigil. Like, the have the streets be that over-crowded Victorian London look that really gives Sigil its feel, but have the interior of many buildings be connected demiplanes, pockets on other planes, or even just have Escher-esque designed inside.1) Ditch the interior of the Donut for a Mobius Strip with the plane constantly spinning toward and away from the twist.
To me, this is what the Gate Towns should be. In my mind, the Gate Towns should literally be Sigil's "suburbs," not just unconnected burgs on the Outlands. Perhaps the 6 Wards of Sigil should be the downtown, and the Gate Towns be the outskirts. You may have to get there via a portal, but they're definitely part of Sigil.2) Less "Go to the Outer Planes" launching-point doorways, more "The Outer Planes are pressed against this reality from all sides". Like still go through doors to get there, but have Sigil itself change based on the current prominence of a given plane of existence relative to the Strip.
Definitely this. I'd be tempted to say that the factions shouldn't actually be part of the government. Faction members can be in the government, of course, but the factions shouldn't actually control Sigil in that way. As it stands, the factions have to play nice with each other or the entire city risks collapsing. If the actual government were more neutral (or "neutral"), then at the least there'd be more conflict between the factions.3) Internecine Conflict. The Factions are cool. Bring them front and center so that even in "Peacetime" there's still a reason to work toward your faction's goals and against other factions... or act as Yojimbo and play them against each other.
Yeah, I'd like to see more things like that. Fewer infinite planes, more "smaller" places.
Actually, the infinite aspect of the planes is, I think, a bit of a problem. Each plane is infinite, but of course the books can only go into detail about a single miniscule part of it. My personal take on it is that the planes aren't so much infinite as they can always be made bigger if you have the strength of body and mind to do so.
That was hinted in 2e Planescape as well, that mortal minds are able to comprehend only a very small portion of the planes and godly realms...They finally explain this in 5e, the Corporeal parts of Outer Planes are finite, it's the incorporeal parts of the planes that are infinite.