Opium Dragons fly through walls as they should they aren't irrlights. They're more useful, everyone wants them so why would they operate the same way? They shouldn't unless you're smoking from a hookah then they should bounce. Because hookahs degrade so fast outside they're kept inside making them a deteriment to smoke opium from cause the dragons will fly through walls off into the infinite abyss that surrounds every interior. You want to give incentive for people to use hookahs not the opposite and hamstring them so they're fun little furniture pieces and nothing more. This way you can do that without fucking around with the stats of anything. Maybe give these dragons 1 or 2 bounces before they fly off to balance it. Thought this would be a unique little inconsequential change that'll add to the fun a bit. I'm sure someone is ready to jump at my throat call me a sprucecap and brag how much more opium he's smoked than me.
EDIT: Because right now the most optimal way to smoke opium is on a horse in a middle of a field. Not quite historically accurate and I know how much everyone loves realism in this game