Well firstly each drug has different melting & boiling points etc. Some wont get hot enough to vaporize in a vape-pen (or whatever you want to call it) and some might get too hot and burn into a chemical you don't want. Also lots of different batches of RCs behave different in my experience. One batch of xxx might burn and vape a certain way from vendor A and the same xxxx drug might burn to a crisp very quickly from vendor B.
I've put MDPV in vape juice before and it ended up working out very well because of MDPVs low melting point/vaporization temp. It also RUINED the top half of one of my e-cigs beyond saving. Beyond that I would wager most RCs would be a waste of time. Even if the numbers worked out, it would have to be very potent per mg to be worthwhile.