Two thoughts, Caleb. One is that you could install the drywall and then put the siding back on the wall up to about a 28" height for wainscotting. You would want to preserve as much of the original look and patina as possible. These could be installed either horizontally or vertically.
Seems to me that I have spent a lot of half hours watching Norm What's-his-name that used to do some TV shows with *** **** building furniture out of old pine and other woods. 4" wide T&G pine might not be good for much other than table tops and maybe table rails but if you had a lathe and some old pine timbers from an old barn or something, you could make some neat antique coffee tables. I know that there are places that buy wood like what you have for similar uses but I don't know any of these dealers.