I had a similar thought. For example, I read somewhere that Padron cigars involve multiple private farms, some owned by the Padron family. I doubt you'll find that on Leaf Only. Some of these cigars are very elaborate in terms of growing region.The thinking behind wanting to explore this path is that single leaf tobaccos that you can purchase are not quite the same as what a cigar is rolled with. A cigar has had it various tobaccos chosen and often fermented to have particular tastes.
The only problem is that the end goal for them is combustion, which will result in a different experience than vaping. Some of that stuff in there is just to help burning. Maybe a vape blend needs a higher ratio of wrapper and binder.
I had a thought though. It seems messy, but I am thinking next time I want to try a cigar extract, I will rip it apart and try to separate the wrapper, binder, filler, and create a separate extract from each one and then try to combine them later. Then I can bump up the ratio of wrapper and possibly completely removing components of the filler. for example.
Maybe that would be a good experiment. Take one whole cigar and put it in one extract, then compare it with the combined extracts of the different components of the same type of cigar.
Then possibly compare that with similar Leaf Only varietals that match the particular cigar profile.