I'm not a realtor but I can tell you that closing off our foyer is the best thing we ever did. All the things that you mentioned as concerns were our concerns as well. We had a house fire and we decided to turn the negative into a positive. We ending up moving the laundry room upstairs to eliminate the hassel of hauling clothes from the main floor to the upper level. We put in pot lights to have more lighting in the front foyer area, the heating and cooling concern was noticed immediately, and although my kids are older, I had one child that I definitely worried about being superman. Although we haven't thought about selling yet, I'm sure it will sell. There are alot of people out in this world that think the same way as you....functionality....practicality. And my husband always says to be happy in the home while your living there. that's what really matters right now. We love the decision we made.