I'm sorry that you think this sort of discussion is pointless and I disagree with you.
I, for the sake of my own curiosity, wanted to know how proficient the average practitioners of Full-Contact kickboxers, Muay Thai fighters, and MMA'ers would be at punching, compared to boxers, if they fought under boxing rules.
I did not ask this question in order to make it seem like I was saying that boxing in any way is even close to being an ultimate proving ground for what is effective in a fight or anything else of the like, I just wanted to satisfy my own curiosity and to know how well any of the skills typically developed by the practitioners of aforementioned arts would crossover into western boxing (for a variety of personal reasons), a question that you answered quite well.
Furthermore, even if someone was a straight boxer, if they were to cross over into MMA, it would be more than likely that their hands would be better than most even though they developed their punching skills in an environment where nothing but punches was legal. If you want proof of this, just consider the fact that the people who are, generally speaking, the best at takedowns in MMA are those who are, generally speaking, the best at no-gi takedowns in an environment where no striking or submissions of any sort are allowed, i.e. wrestlers. Even though they developed their skills in an environment that was not MMA, all that they have to do, after a few months or, at the most, a year or two of training, is to slightly adapt the basic skills that they've acquired in another setting but which nonetheless does carry over into MMA. Likewise for the guys who tend to have the best guard work. So I wanted to know which practitioners from which arts, if they were to cross over into MMA, would be more likely to raise the bar high when it comes to the punching in MMA, much like Mark Coleman did for takedowns in MMA and countless BJJers for groundwork in general.
But my primary reason for asking was in order to know which of the three arts, i.e. FC kickboxing, Muay Thai, or MMA, given their rules, would generally develop skills and attributes, as far as punching was concerned, that would most easily crossover into western boxing. If you think that my question is still silly, then too bad for me.
If anyone else wants to chime in on this discussion, it'd be appreciated.