Some thoughts. I'd argue that the only planes that really matter are the eight alignments (Mt Celestia, Arborea, Elysium, Mechanus, Limbo, Hell, Abyss, Hades) plus Sigil - all other planes exist only as glorified transitional planes. Places you walk through to get somewhere else. You don't really need to build on them, since their entire thing is a blending of other planes as a sort of neutral ground.1. Every outer plane needs its locals. Part of the problem is that they use Angels as a grab bag to fill in the whole upper planes, thus making them generic.
2. Every plane needs one unique thing that can be built on.
3. It cannot be just because it was invaded by bad guys, and you are bad enough, dude, to save the planes.
4. It still has to be built on the same overall themes. You cannot turn Bytopia into a plane of the Abyss or anything like that.
So what can be done?
Angels might be "found" in all planes, but archons, guardinals and eladrin/celestial fey are all distinct beings found in LG, NG and CG planes.
I can see Arborea throwing the planar equivalent of the Olympics (especially since Arborea contains the greek pantheon.) and having warrior tournaments dialed up to 11.
Elysium is all about the good aspects of nature, so you can go there for seeking ingredients to counter a plague or curse. It might also be the primary source of good aligned familiars, given how many of them are animal shaped celestials. So, tracking down the familiar to a wizard or druid who passed away for information might be a thing.