Tanaka or Yoshi?

[Joeking]

Very much depends on what the content is. Quests and side-quests? Content, don't require changes when the battle system changes.

NM's and dungeons? The most they would need would be number tweaks on the amount of monsters and their stats.

New areas of the world? The changes they would receive when battle changes happen would be to the monsters.

So not much would have to be changed.

I think for SE the linear approach is best. Like on the boat to Limsa and Uldah they placed that water texture upside down and created a massive rift in the water, you can see the current moving in different directions causing this graphic error or we can just imagines its a black underwater figure overlooking the mistake.