I think if they do anything it should be to rename the current ones as Savage and create a new set of them that are extremely easy and involve no tank swaps, tethers, precise movements, dive bombs and use full telegraphs so people stack correctly for mechanics.

They have actually already redone some of them. A modern take on the Bahamut fight appears in Cid's memories before Bozja, as well as another version in the final dungeon before EW. They could most likely just take one of those and reuse them for T13.

They also have a modern version of Nael in Ruby that they could use for T9.

I'm not sure about Twintania, but there is at least a hunt version of it that seems stripped of anything difficult.

We also have had some of the others reused in dungeons and as hunts and mobs, such as the plant boss.