Hey - Very happy to help with this project. It's certainly very important.
A few initial thoughts....
1. I think one has to be careful about generalising smoking to vaping. Interestingly, the amount of nicotine required to cause significant saturation of nicotinic receptors is surprisingly small, so smokers are likely taking in more than they need to stave off withdrawal/satisfy cravings.
Vaping topology differs strongly from smoking in many cases. Think "grazing" (vape) versus "meals" (smoking). C-max and t-max are the two important figures. It's well understood that t-max in vaping is lower than in smoking, whereas c-max approaches cigarette values with advanced equipment and experience. Perhaps with vaping it stabilises through the day (due to grazing) and doesn't have the "peaks and troughs" that characterise nicotine in cigarettes.
2. Smokers transitioning to vape tend to be advised to start on a stronger liquid and then "work downwards". I'm not sure this is good advice. What we've noticed in our surveys is a tendency towards a higher power output and a lower nicotine strength amongst all users. This doesn't equate to less nicotine consumed, of course, but probably does signify greater pleasure derived from this vaping style (more visible vapor, more flavor). Sure, some smokers might appreciate the throat hit from a strong liquid, but others would be just as well, or better off, starting on a high power/low nic device/liquid combo.
3. Nicotine is absolutely NOT the only compound associated with smoking dependence. Alkaloids likely play a role, but there's a much wider range of compounds (e.g. the "Hoffman Analytes") which, taken together with nicotine, are likely essential for causing the rapid acquisition of dependence seen in cigarettes. Since the Hoffman analytes are specifically the production of combustion, they cannot (and clearly should not since most of them are highly toxic) be replicated in e-liquid. I'm highly skeptical about WTA liquids beyond the placebo (which should never be discounted, btw). I'm also skeptical about the necessity for high t-max vaping.
4. Following 2 and 3, I believe nicotine is necessary but not sufficient for transitioning to vape: the most important thing is ensuring the vaper gets enough nicotine, has products they can use easily and products that provide enough "pleasure overload" to distance from tobacco smoking. I think smokers should be encouraged to use as wide a variety of nicotine containing products as they need to stay clear of smoking: including smokeless tobacco. The reliability of vape products (including the inherent issues with batteries) is a real problem for many smokers.
5. Some researchers have called for "more addictive vaping products". I'm not sure such a thing can exist (given 3.), but also don't think it's desirable. Nicotine is a substance which seems to have low probability for dependence outside of smoking, and I think vapers often have a better relationship with it than they did when they smoked.
6. There are MASSIVE individual differences as regards dependence and the subjective effects of nicotine on smokers/vapers. This is a really tricky area and is still not well understood or honestly researched.