I agree with everything you've said. However I personally believe it is a larger issue that one might expect, and certainly larger than simply DuoQ's.
I've played in really high elo, I know people who have Boosted and been banned for it. The major wall with the boosting business before was 2 things.
1: It was still difficult to "boost" at high elo even with a Solo/Duo Q because of the MMR reductions in your team (thus the high pricing for Diamond/Plat games)
2: There is a system in place to make sure you cannot log onto someone elses account and boost their account up. Thus implementing a huge risk in doing so for both the booster and the boostie.
Dynamic Q bypasses all their roadblocks and let me explain why.
Getting a smurf to Silver/Gold level is incredibly easy, there are people out there who even Bot accounts, the game is free. Thus meaning even if you get 20 games out of a botted account you still made your money and lost no time in doing so.
2: Now you can get 4- Master players (at exceeding rates but guarantee time preference and no punishment guarantee) to absolutely eliminate any slowing process to reaching HIGH Diamond in League. This is EXTREMELY horrible for high elo players who Solo Q right now, because oftentime these Solo Q boosted accounts do not have friends in high elo thus going directly into high elo and ruining the ENTIRE system from the top down until they eventually plummet down to Bronze/Silver.
3: In a game with over 65million users and give that 90% of the community is Gold below. This problem will become MASSIVE, as there will be no system that can accurately detect Dynamic Boosting without scrapping the entire Q altogether. Now think of even a million players getting boosted to Diamond heights? It literally washes up the entire system altogether. Think about all the games on the way up that will be broken and again all the games on their way down that will be broken again. This adds another level of mathematic variance in the game that is a large variance and there is nothing you can do about it.
4: People do not have to log into other people accounts anymore. What Boosters are doing now is a "teach as you go" pay price. They will teach the low elos how to do exactly what they need them to do in order to continue to climb. It would be similar to a Grandmaster player telling you every move to make playing Chess up until a point where they just get up and leave you to play against other Master Tier Chess players; these players won't have the years of cognitive thinking and skill to even remotely put up a fight.