I agree with you about the caffeine. Needing to add caffeine to a substance in order to vaporize it properly seems like a sign that the vaporization technique or form of the drug should be adjusted, rather than ruining it with an adulterant.
assuming the product is clean, why not use an "oil burner" like people use for DMT and meth? That just seems easier and the only reason I can think of not to use it is if the stuff being vaporized is so full of contaminants that it would fill the oil burner with charred garbage after a couple uses. Like I said, I don't work with these substances but I've gotten very curious lately and you seem to have real-world experience so I'd like to hear your thoughts.
I was also wondering what chemical(s) you use to free base molecules. There's an A/B procedure on Erowid for cleaning heroin that uses household ammonia for the salt to freebase conversion.
From that procedure it looks like what you're doing would be pretty simple. For example:
-dissolve the opiate in water
-discard insolubles
-add household ammonia dropwise until precipitation ceases
-separate and dry precipitate
The mechanics of the last step seem the hardest, unless you simply be patient and dry the solution. I don't think you could dry it in an oven due to the low boiling points of freebase opiates but maybe the ability to dry it under vacuum would justify the expense of a vacuum aspirator and a flask with a vacuum port.
mmmmm... mad science!