"because this seems fair and doable."

What has lead you to determine that there should be a tax benefit to updating a personal residence for personal needs, the place where they have lived all these years wearing out the various parts and pieces? They are investing in the home they intend to live in, and improvements can be part of basis, but not everything is tax deductible. Life is not a tax deduction. Sometimes, it's just how you pay to live the life you want to live. Is there some unfortunate condition that they are contending with, such as a medical lift requirement?