So first we need to unpack the implicit assumption in your statement. First there are 100 cannabinoids (I think that number is high), that they are all in every plant, that they are at levels sufficient to make an impact, and that impact is a positive one. Thats a lot of assumptions that I'm not willing to make.
There are just so many variables here that its hard to truly parse into useable information. Add to that the consumption method, addition of terpenoids and flavonoids in varying quantities, and the problem seems insurmountable to be clear on what causes what.
So let's say you wanted to see the effects of THCV. You could, as I showed pics of previously in this thread, take a bud ("full spectrum", but what's in it?) and add THCV to it and smoke it. Basically you are getting everything that was in the base plant with a might higher concentration of THCV. If you know the effects of the bud by itself, you can start to test theories about what THCV does and does not do. But you are still limited by what the base plant has in it for the full entourage effect.
Take it to the next level - do an Ethanol extraction keeping the sample temps below 40*C - and you have a full spectrum concentrate (undecarbed). You could then add stuff to that in varying quantities and see the result.
Next step, perform the Eth extraction on your 5 favorite plants. Combine them. You now have the complete cannabinoid and terpene profile of 5 plants, all of which have varying amounts of the ~85 cannabinoids (many will still be at undetectable levels). Now you are starting to get to a base that is much closer to what I think you are describing.
Here's where it gets hard - you have to select and grow plants that have varying makups. That is not easy, because seemingly all the breeders out there are looking for that high THC spike to the detriment of all else, which is in general the plants we are all talking about. Look at Milson's TLC - those giant blobs are THC. That is representative of 99% of the testing I have done and seen done with the genetics we are working with today. This high THC and little else result from breeding leads to what many call a boring high. But high it is, so it sells.
What about going back to landraces and finding those truly unique cannabinoids in detectable levels. Combine those. Then you can use the isolates to dial in percentages of the big cannabinoids - THC, CBD, CBC, CBG, THCV, etc. That goes for terps too.
What I am describing is a short cut to breeding. And more importantly, you can go off the rails trying to breed that one thing (like THCV) and screw up the proportions of other good stuff in the process. I submit that a single plant will never be as wide a spectrum of molecules as the process I have outlined. And what if, after your years of breeding for a THCV spike - you get the same result as today's commercial pot. A heavily skewed plant towards one cannabinoid. And what if we know that CBD and THCV work together along with other molecules to reach the desired effect - and your newly minted genetic masterpiece has no CBD? Do you claim THC Victory and sell the seeds that produce a plant that has limited effect? Marketing 101 says yes.
There may come a time when all these interactions are fully understood, and a plant so perfect in every way is bred to contain exactly what is needed (which of course will vary by the person consuming) but I am not holding my breath.
Yes, I get that what I am proposing is both foreign and in many cases uncomfortable for people to embrace. But it's what I do as an engineer. It's not that different from metallurgy in all honesty. Add a small amount of chromium to carbon steel and get stainless, a completely different yet equally useful alloy. Add too much and you ruin the result. Not enough, same problem.
Somebody will figure all this stuff out eventually. For right now, might as well be me, I got nothing else important going on!
My last thought before I jump off my soap box - how do you know that THCV (or whatever you are going for) will actually do the work inside you that you hope to get done? This is what I want to flesh out with my known qty of different molecules. You know all the things that CBD supposedly cures? Hell they even put it in pet products now. I call BS in my gut, but I don't really know unless I experience it myself, right?
The scientific method is an empirical method of acquiring knowledge that has characterized the development of science since at least the 17th century. It involves careful observation, applying rigorous skepticism about what is observed, given that cognitive assumptions can distort how one interprets the observation. It involves formulating hypotheses, via induction, based on such observations; experimental and measurement-based testing of deductions drawn from the hypotheses; and refinement (or elimination) of the hypotheses based on the experimental findings. These are principles of the scientific method, as distinguished from a definitive series of steps applicable to all scientific enterprises.[1][2][3]
To which I would add that once a hypothesis is proven, another must be able to duplicate results or it is rejected. This is doubly hard when the thing you are testing is your own brain.