Expedition: general discussions.

In general, I sometimes have unexpected thoughts, and here's what I came up with.
We've had expeditions to different worlds, fantasy and not only, and now we're reaching a new level in Koshi's world, conquering galaxies. So, is the idea for a setting that takes place outside of time and space viable in theory? In other words, traveling between worlds. This could include fantasy, ancient countries and continents, modern worlds, the future, post-apocalyptic settings, all with their own civilizations, inhabitants, and, most importantly, diverse environments.
In some places, magic can be used normally, in others, they've never seen laser swords, in some places, an elf would be burned at the stake, and in others, you'll die from radiation without a protective suit, and so on.
To tie this to some kind of balanced storyline, like portals between worlds aren't that easy to open, and add all sorts of cool demons that aren't just universal evil, but simply on par with the others, and add all sorts of interesting features, etc.
In general, since I might get tired of this idea already this morning, and it probably will happen, I just want to ask for your opinion, how interesting and feasible is such a concept? It's probably too complex and there will be a lot to think about, but overall, does it deserve attention or is it just nonsense?