A not-wholly original concept · 6:52pm Jan 17th, 2014
This occurred to me this morning as I was heading out the door to go to class: an AU where everypony has switched places with their opposite in the overarching meta-plot. That is, Luna had to banish Celestia to the sun way back when, and the roles of the Mane 6 are being filled by Sunset Shimmer, Suri, Lightning Dust, Cheese Sandwich (maybe?), and... I don't have any solid ideas for AJ and Fluttershy's replacements yet. The idea's not going to be fully developed until Season 4 is over and I find out if my theory about the box and keys is correct. And I'd need to finally watch Equestria Girls in order to get Sunset's character down right.
This idea is partly unoriginal, because I've seen plenty of stories based around Celly and Luna switching roles in the past and/or alternate Elements of Harmony Bearers.
What I haven't seen much of (mostly because I don't browse very often) in Sunset Shimmer in the Element of Magic role; it's usually Trixie.
Obviously, Suri and Lightning Dust don't really demonstrate Generosity and Loyalty, and haven't gotten good vibes about Sunset's friendship-ness, so there may be a reason to change the Elements a bit. I'm also unsure if Cheese Sandwich would make a good part of the group - not because he's a stallion but because I'm doubting he'll be as strong an anti-Pinkie as Lightning and Suri are to Rainbow and Rarity. The biggest issue, as previously stated, I currently have no candidates for Applejack and Fluttershy counterparts. I'm hoping the show provides those in the near future.
World concepts like this never come to me without a plot idea. This one's also been done before, but the idea that came to me was this AU group crossing into Main-line Equestria (most likely NOT my Order-naries version if I can help it) either due to a mishap or intervention by Evil!Celestia during the search for the EoH. Taking time to develop the AU and why it's Sunset and those others rather than Twilight and company would be a wiser starting point though.
I think I remember someone discussing a similar concept in site IRC a while back. Something about the "original mane 6" if SS had not bailed and Twi had not had her Rainboom-fueled overload.