Most of it has been in use for decades and isn't in prime condition. Radiation embrittlement, micrometeorite impacts will have weakened it. Not to mention lacki

Most of it has been in use for decades and isn't in prime condition. Radiation embrittlement, micrometeorite impacts will have weakened it. Not to mention lacking the benefits of decades of advancements of material science and the ability to test components together on the ground. Not being able to take advantage of lessons learned during ISS design and operations. And having to tie your design to parts that were designed and manufacturing in a previous century. That are probably not capable of being certified against today's standards. I don't really see it being feasible. Better to just clean room the design based on today's knowledge and tech. Heavy lift is getting cheaper and cheaper anyway.