Yeah, I think they've tried everything there is for that airframe. I think I even saw a picture of one on floats. I propose putting a couple of JT8D's on it...
I flew ones with JATO bottles on the belly centerline at the trailing edge of the wings. The theory was that with an engine failure, the JATO would help the climb. Upped the GWT from 25,346 to 26,870 #.
The airplane will still be around 30 years from now.