Hi Steve
A 12 inch F8 newt would be a nice telescope but very long. One more exotic option you could consider is Ed Jones' Chiefspiegler. It's like a catadioptric herschelian. Many of Ed's designs can be built with off the shelf lenses. The folded nature of the design would mean you could avoid using a ladder. His web site is here:
http://home.fuse.net/eljones/
Sorry I don't now what your mirror was used for. The mount makes me think of a coeliostat (solar telescope) but I don't know enough about them to be sure.
Rod