Having the 'original' Surface Book, I would love to just upgrade my base (keyboard and ports) and keep my current screen (CPU, RAM, Antennas). I don't see why

Having the 'original' Surface Book, I would love to just upgrade my base (keyboard and ports) and keep my current screen (CPU, RAM, Antennas). I don't see why they can't sell screens and bases separately. This would be a huge plus if I could upgrade different parts of my laptop.