I honestly don't think you'll be able to find a publisher who would be willing to go hands off on the online revenue(whether it's fair or not) for a couple reasons:
(1) As far as they're concerned, they're taking the biggest risk by laying out all this money ($2 -4 million dollars is alot, even for big publishers, EA grossed over a billion dollars last year and still posted a loss) and therefore entitled to share in all profits.
(2) The quality of the online service is directly tied to how well the game will sell. If you screw up ( I'm talking from the company's exposure analysis, not trying to slam you) on the server side, and people know it, they won't buy the game.
Worst case scenario, the site goes dead after three months, everyone grabs their already opened boxes, and takes them back to Electronics Botique and demands a refund. Electronics Botique gives them store credit and demands credit from the publisher. Now the publisher ends up taking a hit on something that they thought was closed out and profitable. Gamers will also hold the publisher responsible for years to come even if they had nothing to do with it. I know at least Activision's SEC filings lists returned products/retailer relations as one of the risks of the industry right up there with missing the Christmas window.
Back to the client. I don't think that a website is the only way to get copies out. One is OEM channels. A hardware company comes out with a new product and tries to manufacture a market for it, and bundles software to show it off. One of the ways companies are trying to sell DSL(which I just got, downloaded the Kingpin demo in 25 minutes) and other broadband services is Online Gaming. If you get US Robotics to throw the game in with their DSL modem, it'll get delivered straight to people who want to see what this puppy can do. You might even be able to get a few bucks.
Does anyone out there know how the deals go for the Demo CD's that get thrown in with Game Mags? Are publishers paying for the privilage, or do the Mags negociate for exclusive rights? I imagine a little bit of everything goes on but what is more prevelant?
Glad to see you're considering giving the client away.