I think it might all boil down to how much ability you and DH have as do-it-yourselfers. I have a '78 HR Statesman 27 foot and a '79 HR Imperial 5000 32 foot, and I love them. I bought the '79 as a fixer and will have less than $3500 in it when I'm finished. They're built like tanks. I expect them to be going strong at 50 years.
If the trailer you are considering is in decent shape, there is very little you can't repair or upgrade. Especially if you are able to do most of the work yourself. And when you're finished you have a custom trailer that is a classic. But if you're going to have to pay to have all of the work done, I think you'll be better off buying a newer trailer.
JP