I use bullhorns and sometimes have the hairbrained idea that it would be nice if I could adjust their height quickly and without tools, even while riding, like when turning into a very stiff headwind or for a very high position for a casual cruise.
Something like a lever than can be pulled by both hands while at center most position of top of bars, that releases ratchet so the linearly adjustable vertical part of the stem (inside the steerer) can be slid up and down, say with 4" or so of travel. It would be keyed so no rotation would be possible.
Obvious cons: Accidental release, added weight, added complexity, potential lost stiffness
And yes standard drop bars 'solve' this need without any added complexity.
Sure its easy to argue why a silly idea, but I wanted to share anyway. Maybe its even been tried, but I couldn't find anything with a quick internet search.