Just a curiosity really, but would this crazy idea work...

Threadless fork, install a really deep star nut, use a long bolt to pretension and clamp a stem on as usual.
!Then, remove the pretension bolt and top cap.
Install a quill stem into the fork above the existing threadless stem.

(yes, Im aware that this would require dissasembly for future headset adjustments)

So, how well would that work? Quill capable of supporting handlbars and associated weight? Threadless fork capable of supporting quill wedge without wall deformation? Etc....?

Possible applications include:
using the normal threadless stem as headlight mounts
poor-man's stem riser
frankenbike points