If you don't want to go through that rigmarole, tell them you've been told it isn't possible to do it - they'll soon prove you wrong by doing it. But old skills are being revived. I believe that by reusing salvage, we're rescuing them as well. It encourages craftsmanship. Old materials on old properties will not only feel right, but they'll also blend in more easily because of their 'weight'.
Many new materials are heavier.
Putting more stress on a tired, old building could cause the roof to have a breakdown, and you to have a nervous one. One of the areas where, with a bit of ingenuity, you could save yourself a bit of money is to build a glass extension. On my travels I've seen some rare extensions and one particularly sticks in my mind and makes me smile. A retired scrap dealer tried to sell me his add-on which housed his swimming pool. It was hilarious - made from corrugated sheets, aluminium windows, the diving board was an old scaffold board.