The idea I have, and have slowly started to flesh out a story for, is basically a time travel one. It would incorporate three distinct time periods:
1) A Mystical "past", where sword and sorcery type action happens.
2) a Political "present", where modern warfare action takes place.
3) a scientific "future", where space based action takes place.
The basic premise is that there are three factions on a planet, a "good" side, a "bad" side, and an independent, mercenary, rebel, type group. The major cities would have "time capsules" that let people transfer between times. The character's clothes and carried objects would change to match the current time frame, but a very good weapon in one time might not change into an equally good one in a different time, and an inconspicuous item in one time frame may become something incredibly powerful in another time.
There would also be "anachronoistic areas" where PvP combat would take place. These would be the moon and an alternate plane, acessible only in the future and past respectively, but both would exist in all tree times (you can't leave the moon in the past, you'd have to transfer to the future to get back down).
Skills, experience and levels would not transfer, the only thing that would remain constant is your loyalty to one of the three factions vying for control over all three time periods. So you could max out a character in one time frame, but be completely weak in the other two, or any other combination.
Like I said, I'm only slowly fleshing this out, but I was wondering if anyone else thinks this could be fun, or would it just be too much, either alienating people who prefer one type of role playing and not another, or do you think it would necessarily lack development of each time frame due to size and speed limitations?
I'm not a programmer, and while I think the premise sounds cool, I have little to go on as far as practicalities.