Good Idea? Your Opinion.

[Sylve]

it's making us go back to 2.x during an expansion cycle, an expansion that we paid for and most likely expected to do new content with.

Personally, I don't feel that this is a good mentality to have for an MMO. Completely invalidating all previous content just because its part of a previous version of the game just leads to WoW.
I say that because that's what WoW does. Outside of the more recent Timewalking stuff, no WoW expansion ever gave you reason to leave the new Expansion zones.
With ilvl Syncing here in XIV, we'll never run into the issue of quality content like Coil being rendered completely worthless in the future. I could get a freind into the game in 6 years time and then take them into Coil for the exact same experience that the bleeding edge raiders had back when Coil was the peak of raiding.

Giving us a reason, however contrived, to revisit older contents is a good thing for the game. How they go about that though .. Thats a whole different kettle of fish. But just claiming we should ignore everything that came before is unhealthy for the game.