Halting the McMansions

Boulder, CO, may have come up with a solution to the gross problem of McMansions:

"Homeowners willing to sign away their option to someday add additions to their houses would receive a one-time payment as well as lower yearly tax assessments on their homes. The forfeited enlargement rights would then be available for purchase through a specially established market. Residents planning to build or expand homes larger than the recommended thresholds — 7,000 square feet on the plains, 5,000 square feet in the mountains — would be required to purchase additional development rights at prices determined by the market, which might be in the hundreds of thousands of dollars per property."

5,000 square feet! What would you do with 5,000 square feet. Right now The Poor Man and I live in a townhouse that is just under 1,000 square feet. I would love a kitchen and living room that are twice the size we have now, a master suite where our bedroom is about 1.5 times our current bedroom and a walk-in closet, and another bedroom and bathroom. So that would be 3 bedrooms and 2.5 bathrooms total. I expect that would be about 2,000 - 2,500 square feet. What would I do with 5,000 square feet of living space?? Even if we had 5 bedrooms (an office for the husband and a craft room for me), that would still not add up to 5,000 square feet. How do you keep everything clean and cool/warm?