I like the idea in theory, but I worry that it wouldn't realistically work as intended. I do think that at the very least, it should be several representatives per job, and they represent individual jobs rather than the role as a whole since expecting one person to treat all the jobs in their role with equal consideration and experience is a bit unreasonable. I would say that each job should have two representatives per region, with a "Raider" representative to view things from the viewpoint of those playing the hardest content frequently, and a "Standard" representative to view things from a gameplay standpoint that the average player would look at, since those who raid, and those who don't raid tend to have very different outlooks on what is needed for their job, and how changes will affect them......
SAM is a good example in that regard from the early previews, since it appears to be geared more towards having high enough DPS that it is still usable in raids even without utility skills, but more than a few players are concerned that its personal DPS will be too high in standard content as a result. Having a representative for both groups would make it so that there is less of a chance that one would skew the gathered feedback to suit the type of content that they prefer. I also think that it's important to have representatives from each of the major player regions as well, (JP, US, EU), since the community for each region is very different in how they approach the game, which could mean very different outcomes depending on where the representatives are from if they're not equally representing each region.....
The main question after that though, is how would these representatives be chosen, exactly? Leaving it up to player voting might not be the way to go in this sort of situation, both because there is the chance we'll see the ones with extreme view points being loud enough and vote more that someone with a very skewed opinion might get into the position, and because the alternative is that we'll likely see someone with a strong following that can simply get votes from them, (such as a Youtuber), end up in the position, rather than someone who would actually do well in the role. The only reasonable way to have the representatives be picked and remain at least semi-neutral is by the dev team, but then how would they be able to judge who would accurately represent the classes in question? Raw stats or play time wouldn't be the way to go, because it wouldn't necessarily indicate that someone would do a good job as a representative, but at the same time they can't exactly go through and read all the posts everyone on the forum has ever made to determine who would fill the role best from a social and reasonable argument view point. I'm honestly not sure what the best way of even choosing representatives who are actually qualified for the positions should be. Either way, the representative has to be someone who actually plays the game, and class in question, because they are the ones who would be testing and ensuring that changes are actually what the players would want, rather than just sounding good on paper......