I just think it's silly that, in a system where players are already casting the same spells over and over, implementing an elemental wheel to add a little more sense and context to the job is considered a system where players will just cast the same spells over and over. Seems like a redundant argument either way.
I want an elemental wheel in this game. Why? Because it makes sense, given the amount of focus on the six major elements: Fire, Earth, Wind, Water, Thunder, and Ice. There is an elemental themed boss for each, there are crafting crystals that are attuned to each of those elements, there are spells for every element currently in the game, and there is already a resistance attribute for every element.
It wouldn't break balance if it was done right. BLMs are already counter-balanced by the fact that they're the only job that can't DPS and move at the same time. One may argue Summoners are in the same boat, but let's face facts: Summoners use DoTs, half of which are instant-cast, and they have pets. So if they have to move around, their DPS isn't going to take nearly as much of a dip as BLMs. But ultimately that's a different discussion for a different thread.
The fact of the matter is that BLMs, as they are structured now, are slaves to a single rotation. Fire -> Transpose -> Blizzard -> Transpose -> Fire, while throwing in the occasional Thunder. That's pretty much it. It's boring as balls and allows for zero variation regardless of combat situation. So if there were an elemental wheel, that would at least allow the BLM to change it up depending on the situation. Make some spells more powerful in some circumstances and less powerful in others. BLM should not be a mindless job, and yet it can be one of the most mindless because the rotation has minimal variation.
Why not give a BLM spells which gives an enemy a temporary weakness to a specific element or nullify elemental resistance? Something synergetic. Like, if you use Fire three times on an enemy, it makes them weak to Blizzard spells, or if you proc Thundercloud, it makes Thunder spells do more damage per tic?
The elemental wheel is very important, but getting back to the original topic, BLMs just need to be less of a blind, mindless DPS job and more of a magical DPS job. The "Batman" of magical DPS, if you will. Just someone who can see an enemy, be like "I have just the spells for this! Stand back!" and unleash a torrent of hurt specially picked out for the enemy in question. Blindly swapping back and forth between the same two kinds of spells is mindless and boring.
tl;dr: Elemental Wheels should be in the game, but should be done right. Ultimately, BLMs need to stop being a mindless job and should have a lot more utility.