Wouldn't conduction vaping be possible and even preferable to convection vaping if you had the perfect thickness of glass between the flame and the spice?

I'm talking glass thick enough so that the hottest the flame could ever get the other side to be could only have to potential to vaporize without burning. Obviously lightbulbs and aluminum foil are too thin for this, which is why they don't work so well.

This way, the "one hit with everything" idea is possible.

I don't really know about preferable but that other dude has used a glass jar which contained some kind of cooking sauce like dolmio to vape sticky syrupy jimjam. It withstands heat pretty well, in a factory setting these jars are put under quite a bit of heat in sterilising and filling, but even on a small gas ring it takes time to heat the jar and make the jimjam runny and it vapes quite slowly. He initially tried with 2 tea lights underneath it to get a trip on but it's very slow work.

He only really used the gas ring on the cooking hob to warm the sticky syrup enough to get the remnants of a pull out of the jar in order to vape the majority of it by other means. Now the jar wasn't in the flame, it was slightly above. It wouldn't make sense to try vaping it over a gas hob, it's not the right place lol but during the warming for removal it did begin vaping.

The bottoms of these jars are quite thick, with enough sustained heat I suppose it could work ok but not a 1 man job because of the amount of heat you'd need to put into thick glass, it cools rather quickly and dissipates throughout the jar so it takes time that other dude couldn't afford. That other dude hasn't tried this method extensively due to neither having help nor adequate heat source and resorted to foil and bottle, with great solo effect, for faster heat delivery.

The problem is that when one removes the heat source, the glass stays hot. For this reason, accurate temperature control is nearly impossible when using a conduction vaporizer.