It should be possible, but inconveniemt. You could use a locking collar in place of a threadless stem, to hold the headset together, and then fit a quill inside the steerer while avoiding whatever device you used to preload the headset. You'd need a substantial shim to fit a stock quill stem. It seems easier to make a threadless stem to your requirements. It's hard to see how combinimg the two types is better than a threadless stem, threadless is a superior system.