So out of interest, how would you give tanks mechanics to deal with that are not tank swaps? This is just out of interest as i see no problem with tank swaps being required in this game, so are interested in how raids could deal with involving tanks in mechanics specifically for tanks if tank swaps were not part of it.

Also wih the elemental issues you point out. If they introduced elemental strengths and weaknesses into the game that matter, the game would have to be fundementaly redesigned to accomadate this. WHM are the ones who have access to wind water and earth elements in game, BLM having fire, ice and lightning. BLM would be useless vs ifrit in its current design and also useless against shiva.

Also all Final Fantasy entries in the series always change how mechanics work in the game, how elements work and how the various classes work. 9 and 10 had the WHM who were also the only ones who could summon primals. 7 and 8 had no class designations (except maybe tenuously the limit breaks in 8 giving some class division). 12 doesnt have the traditional summons or classes at all, anyone can do anything. 10 anyone could eventually use any kind of magic in the game.

Final Fantasy entries have always changed their own in game rules and lore per entry in the series. Same with 14, it has developed its own set of rules and lore within the Final Fantasy Universe.