I can’t see where your assumption of a saving derives from. You are more than doubling the labour content of the build, and whatever savings you’d make from not buying all the materials would probably be eaten up sourcing small quantities of materials no longer readily available to replace inevitable losses of the originals.

But honestly, I am guessing as much as you. I can’t claim specialist knowledge.

Your guess is much more accurate.

Moving an old hangar is an emotional thought, not a rational or realistic one. As said it would cost a LOT more, take a lot longer and plus you would end up having to replace so much of it anyway to make it compliant in todays world (especially as this is going to have to meet public access regs) that it is just a pointless consideration.