I say a mix as well, but the overlyling theme is teams. Here's how I would lay it out:
Main event:
Elimination Chamber: Have one every year just like the Royal Rumble, and switch between the 3 titles (or 2 if the ECW title lasts that long) to be the contest. For example, this year have Randy Orton in the chamber against HHH, Shawn Michaels, Umaga, Mr. Kennedy and Jeff Hardy.
2nd Main Event
World or WWE Title Match
You have to defend at least one main belt, so for here it'd be Undertaker vs. Batista for the World Heavyweight Title. They may have either a cage or HIAC possibly, which takes away the Chamber idea, but why a ladder match or some similar gimmick?
3rd Match
Women's Title
Oh, give Beth Phoenix a match. Space between the Tag matches is needed anyway.
4 matches of the Survivor teams
1st match: Brand vs. Brand team
Whichever brand holds the Elimination Chamber, have the other two brands face each other with an elimination tag match. My example would be Matt Hardy, M.V.P., The Great Khali and Kane vs. C.M. Punk, Big Daddy V, John Morrison, and The Boogeyman.
2nd match: Midcarders
My best example is from ECW: Tommy Dreamer, Balls Mahoney, Stevie Richards and James Curtis vs. The Miz, Elijah Burke, Kevin Thorn, and Matt Striker
3rd match: Mid carders
From Smackdown: Rey Mysterio, Ric Flair, Chuck Palumbo, and Jimmy Wang Yang vs. Finley, Kenny Dykstra, Mark Henry and Chavo Guerrero
4th match: Tag-Team Midcarders
From RAW: Hardcore Holly, Cody Rhodes, Paul London and Brian Kendrick and vs. Shelton Benjamin, Charlie Haas, Trevor Murdoch and Lance Cade