I actually think it would be a good idea if it was expanded on. It's no different than a controlled beta testing group. But I think it's also key to keep in mind that the purpose of that program is to provide detailed feedback. In no way is the team from ESO obligated to follow that feedback (nor do we have proof yet that they will). It would also have to be made public like ESO's will be so that the rest of the community has a chance to comment on said feedback (which then brings up the question of where said feedback gets posted).

I also share a similar concern that post #20 on that page comments:

While I do welcome some open discussion, I feel that one point needs some clarification. Should these representatives just collect and compile the concerns of the community posted here on the forum or via other channels and discuss these with the devs so you don't have to read every single post, or is this an invite for people with in-depth knowledge to bring up points they think are an issue with that class?

If it is the first, I have to say that's actually a bit lazy and insincere since that should be a job for someone working at ZOS and not for unpaid volunteers, if it's the latter, it might easily turn out to be a bad idea since every one of them will have their own agenda and they likely won't provide objective feedback. In either case it could easily happen that a huge part of the player base and play styles gets underrepresented - especially since people with in-depth knowledge don't think or play like more casual players which should make up the larger part of the community.

Maybe it would be better to instead start using some platform like uservoice so everyone can participate and you can easily keep track of what's been requested?
The post introducing the program is very vague about what you're expected to do. Not to mention throughout that thread alone there's already disputes within that community over who is actually qualified to apply and who isn't. I can't imagine this forum would escape that as well.

If SE were to do this for FFXIV, then they would have to get more specific regarding what they want from such representatives and then be open about it. Not exactly fair to expect even loyal fans to sign up for something without telling them what that something actually is.