Need a way to retrofit zoned heating into forced hot-air homes

Let's face it, we had our energy wake-up call 35 years ago, and we have continued to live pretty much exactly as before, instead of making changes, some of which might have been more disruptive (less driving and driving alone), some of which seem like they would have been fairly easy.

In the latter category I would put: building houses to be more energy-efficient. I am a notorious home-thermostat nazi, but even I get tired of being chilly in my own house. But I just can't justify heating 3000 square feet, when only one or two people are at home (I work from home 2 days/week, so that one person is often me). The design question is--why do I have to choose between the extreme of 3000 chilly square feet or 3000 warm square feet? We all know that we tend to use 1-2 rooms of the house most of the time, typically the kitchen and the TV room. Why can't I close those off, and have zoned heat that let's me keep them at 72, while the rest of the house cools down to 60?

As I noted, if we had any brains at all, we would have been building houses to support this option, lo these last 35 years. In the absence of that, we need a way to retrofit the typical, suburban forced-hot-air system to support some heating zones. But there would still be the problem of doors--retro-fitting them into my floorplan could be physically done, but it seems like it wouldn't look so good.

(Yes, I know, we also shouldn't have been building 3000 square-foot houses, either. I agree. I would like to trade mine for a townhouse.)