But what about scope creep or changes in expected costs? What if putting in X feature was projected to cost Y zots and would, therefore, require Z number of supporters, but then the price goes up to 2 * Y? If the feature has to be cancelled, what about those players who suddenly don't want to play the game at all anymore?
Or what about the implementation? You may say you want Bioware to go to a silent protagonist, but they may implement a PC with no recorded dialogue, but still plenty of auto-responses for your character that invalidates your expectation? We've seen these complaints for some Kickstarters, where backers are getting what they were promised, but simply not in the manner they believed.
I like the concept, but the nightmare of its implementation would wake me up in cold sweats if I thought about it too long.
Scope and budget creep are problems that exist today. They could be dealt with in the same way they are now.
As for the preorders, the money would need to be refunded if the feature wasn't delivered. If it was delivered and people just didn't like it, tough. Isn't that basically what happened with DA2?
There would be some risk for the buyers, just as there is now. Again, this isn't a new problem.
The developers would, have a greater PR incentive to disclose feature details. Like how the writing style in Dragon Age changed to accommodate the voiced PC, they would want to explain those things. And if they think the voice-overs genuinely improve the game, they should promote that benefit.