Can't you look at your puffy, hundred-year-old windows? Are they threatened with liquidation? Look for suitable alternative windows. Maybe the right thing for you will be plastic windows.
In the current market in the field of building industry there are many companies and companies that will make custom-made and supplied plastic windows, doors. If there is an atypical window of roof, attic, dormer in your requirements, there is no problem at all. It depends on the agreement and the possibilities of the company.
Others matter only to you. You select the Company, select the window type, the door, the correct dimensions. You determine all parameters, conditions and requirements in a timely manner and take them into a contract of work and work. Don't compromise your claims, you know you don't buy plastic windows every week and they'll be here forever.