I think one of the biggest problem I see with this is that there really wouldn't be that much of a price advantage. You cite $400 as the price for a HD DVD player, yet you can get one for ~$240 right now (or a better player for ~$330). And I can practically promise you that if Sony put out a $150 Blu-ray player, those HD DVD players would be even cheaper (even w/o such a player, there are rumors that we'll see some <$200 HD DVD players this year). I don't think that is enough to end the format war, especially since we're not even sure if consumers are really that willing to go with HD movies even if the players cost $15.
Oops. I didn't know you can get a HD DVD player for ~ $240. You're right - it's not enough of a price incentive. Well, my idea would have been pretty good about 9 months ago.