It didn't work 'beautifully' in XI (though it could have). All that actually happened was for some reason almost all mobs were weak to thunder and/ or blizzard, which worked out well for BLMs because those were the 2 strongest elements anyway (I think in the past few years they normalized things though). Melee just used the water/ ice skillchains while leveling, and then the light or dark skillchains after 75. For skillchains it was a bit more interesting. For casting, and I have played BLM heavily in both games, it was no more interesting. Really XIV is more interesting for BLM endgame because you do a lot more than concentrate madly at the screen waiting for the boss to do something that you need to stun immediately. On the damage side, level 60 BLM is way more interesting than BLM was in XI. Sure you had a ton more spells, but you'd never use most of them and mostly just sat around casting the same spell forever or waiting to stun (or mass sleep things in dynamis).

In any case, they're vastly different games and without some sort of toggle to just change fire spells into whatever other element for the exact same effect (and what would be the point in that?) BLM would be neutered by an elemental resist system. If it wasn't then the system would be too mild to matter (or everything is weak/neutral to fire or extremely weak to ice).