Very interesting gun!
I think I know exactly what I'd do with it.
I would check it out carefully to make sure the frame and slide are o.k, then probably use it to build up a "sleeper" competition/carry pistol replacing the barrel and whatever other internals could use an upgrade. (Didn't the 1991A1s have plastic triggers & such?)
Once you deal with the fact that its factory finish and smooth lines are "ruined" it does have a certain organic beauty to it. Kind of like a George Nakashima table with straight, man-made lines that abut flowing natural features like live edges.
I wonder if it could be stripped, maybe wire-brushed and hit with naval jelly to kill the rust, buffed as-is, and re-blued? No, no...CLEAR COATED! Just consider it an unusual surface finish, like some weird etching design.
I'd build it as a "Rat Rod" pistol. I have friends into the RR hot rod scene and they would vote both thumbs up on the style, for sure. The grittier the better, but with great internals. I'd even keep the grips and safety, etc. Now to construct a distressed black leather and barbed-wire holster for it!
-Sam