Brainstorming a new campaign

The grassroots movement has taken hold, and I've gotten my regular players interested in switching from a 3.5 to a 4th edition campaign. This is admittedly my idea-- I'm a sucker for new systems, and always eager to try the latest thing. But! In my defense, we meet infrequently, and I've only got a little over a year before I head overseas again. I want a chance to play with the new stuff before I'm out of Metro range. And besides, if we don't like it, we can just pick up the old characters a few levels later for the great "reunion" adventure.

Of course, this means it's time to brainstorm for campaign ideas. I'm still planning to run with the Eberron setting since I have all the books and the players are familiar/comfortable with it. But which part of Eberron?

• A campaign in the Lhazaar Principalities would allow me all sorts of island-hopping adventures-- I just have to promise my players that I won't overuse the "pirate chic." I've run an island based campaign before-- there's something in the geographic constraint and intricate ecology that appeals to my DMing tastes.
• A Droaam or "monster" campaign could be fun reversal if the players are up for it-- Droaam has been a source of antagonists for their current characters, and I think they'd appreciate the inversion. However, I don't know that they're as into gnolls and ogres as I am, so that's a long shot.
• The capital city of Thronehold has gone completely unremarked in our campaign, and that's a shame. The palace and vaults of an eight-century-long dynasty just sitting there locked up? Who's got the key? What's going on behind the doors? Who'll feed the Corgis? A campaign there could really explore the political aftermath of the Last War, and put PCs in a central position to determine the future.
• The party has already visited Sharn a few times-- maybe they want to do a strictly Sharn campaign. That'd demand a better written cast of NPCs from me, but urban adventures lend themselves pretty well to improvisation in terms of plot (it helps when there are genuine monsters in the sewer).

Or maybe the players will tell me something I haven't thought of yet.