How can i put this softly, this seems very stupid. Why do you want to put more weight on a dev team that is already full with issues with the current balance of the game, adding this kind of diversity will not end up being a solution but will bring more issues. Now what if, and entetain the thought for me on this- what if i dont want to play dancer? but because this theoretical fight makes it geared towards bringin a dancer instead, no one would take a MNK, so just by doing this, implementing this incredible asinine idea, you just killed a possible composition and you blocked Monks from playing this theoretical fight. So now instead of just balancing How dps do the dps-ing, now you have to balnce how the fights play out with each posible combination and how to make the fights better for some jobs better than others, and then you would have to make a new raid just to fit the ones left out. It seems an awful lot of work to just implement an idea that is 100% pointless, having options is always an ilussion because the goal of this game fights is to deal as much dmg as fast as you can, there is no other goal. If there were other goal then this would be a different conversation, and even then it would be heavely prefered whatever it is that can reach the goal faster, be it dps or doing CC or etc.
Allow me to tell you a fantastic phrase "Given the opportunity players will optimize the fun out of a video game" This is why grinding exist in video games, this is why BnB exists in fighting games and so on, so you just want the ilusion of choice, so you can pretent you can pick up what you want, but in reality you will pick what is better for the goal and as i said before the goal in this game is dealing dmg. Finally, having classes that complement each other is a stupid idea becuase it fosters certain composition over others (and not even the meta world) that is a stupid notion when you have things like NIN being overwermely positive to any party composition, the same as DRG on the support side or are you forgetting what a BRD and DRG comp used to be in HW, amongst others? The only two jobs that are niche composition are RDM and MNK, and MNK even more so than RDM by a kilometer and a half, in fact allow me to tell you this the only class that has never had any synergy with any class (blunt debuff) is MNK. Overall bad idea because it doesnt seem that they are changing the goal of the fights, ohh and just an FYI there were other goals parallel to dmg in the previous raids and people did not like them, ADS on the first turn of bahamut, anyone?