I intend to stick with the so-called "close" planes: the shadowfell and feywild. I like the idea of alternative, creepy versions of normal reality. My shadowfell and feywild will have the same geography as the regular universe, except altered in some fashion. For example, a large city in the real world might leave a reflection in the shadowfell as an extensive series of ruins. Analogously, my feywild will reflect what the world looked like before the rise of man. (Ok, read that, man + elves + dwarves + whatever, you get the idea.)
This way I can make plotlines that revolve around switching between these various analogous versions of reality, and having events which occur in the real world spread like ripples into the others. I can make rules like "planar shifting to the feywild only works if you're in the wilderness, far from large concentrations of iron," or "shifting to the shadowfell works best in areas like graveyards." It also gives me reasons for graveyards to be sanctified, and for peasants to ward their homes and barns with iron: these acts maintain the barriers between worlds.
I've got a couple of brainstormed ideas.
I might run a campaign based around a rising necromancer. His base of operations involves going into the shadowfell for short periods of time in order to complete his Evil Plan. So, the PCs fight him mostly in the real world, with short ventures into the Shadowfell. Eventually, they are too late to stop him, and he unleases a Zombie Apocalypse! Oh no! The real world becomes too hazardous to live within, and the PCs are forced to flee to the Shadowfell for safety, emerging from it to raid and seek items necessary to stop the zombie plague from spreading to other lands.
Stuff like that.
I probably won't use the larger cosmology much. I find that the game works better for me when I focus in detail on a small area, rather than try to encompass a great many things at once. If I DO use the larger cosmology, it will be after a campaign in which the players have become accustomed to the shadowfell and feywild as being sister planes to the real world. That way, venturing out into the elemental vortex or whatnot will feel like going really far away.