So, you want to use a 1" threaded fork, and threaded headset. Then add a quill stem with a threadless adapter in 1"?

I'm not sure what the point would be to use the 1" quill over a 1 1/8" quill. The 1" threadless stems are often hard to come by.

Is the idea to use a 26.0 bar?

Of course, one option would be to hunt for a fork with a really long threaded steer tube that can be cut, or a 1" threadless fork.