Many (even most?) people do have freedom as part of their utility function, but at different weights, so redefinition is unnecessary if you grant a moral imperative to increase the utility of others.
The problem is that most people interpret such an imperative as "increase the utility others would have if they shared my own utility function", which is not at all correct. Simply redefining utility in the general case to include freedom is in this class of mistakes.
Yesterday I heard an interesting story on the radio about US President Obama's pick to head the Office of Information and Regulatory Affairs, Cass Sunstein. I recommend checking out the story, but here are a few key excerpts.
At the risk of starting a discussion that will be wrecked by political wrestling, I'm always hopeful when I hear about governments applying what we learn from science to policy. Not to say that this always generates good policies, but it does generate the best policies we have reason to believe will be good (so long as you ignore the issue of actual politices that might get in the way).