The current system is good partly because it doesn't really replace the presence of players. Too few dps. As a result, a lot of people use the NPCs for a first run, then return to the normal queues. That seems to me to be the perfect balance: allowing a quiet first run, where you can admire the scenery and get into the mood, but without sacrificing community life.
This balance would be broken with the proposed system, because you'd end up with bastard groups that manage to overcome the problems posed by the NPCs. While 3 NPCs can ruin a run because of their lack of dps, it's quite possible not to see as much difference with just one NPC as a healer - thus preventing players from naturally returning to the queues once the first run is over, since they'll be calling on a small circle of friends without having to look for a random player to fill the gaps.
FF has always been excellent at one thing, despite all the faults this forum still finds with it: keeping old content alive and active. It's rare, very rare, to have a game where a raid over seven years old can be launched in 15 minutes. The system proposed by the OP could have a very strong impact on this aspect, and not a positive one. And on this point in particular (since the previous pages quote WOW), WOW remains far behind FF. Which also explains why the proposed system might work on WOW, but not on FF XIV.
To add one last thing: I can well understand why people don't always want to push the community aspect. FFXIV lends itself very well to the single-player experience, so the game only has itself to blame if it attracts that type of player. That said, I find it a tad odd to want to avoid the community to the point where you only want to play between selected people. And at the risk of not just making friends: wouldn't co-op games be better in this case? Because as much as you can open doors to facilitate the single-player experience, if you go too far, as with this type of claim, you can completely destroy the 'MMO' aspect.
Just my two cents - I'm not even sure about the last paragraph, it's just my opinion based on many years of playing this type of game. Not to be taken as an indictment of single-player gamers.