I feel the abyssea type of raid system worked out very well for FF11. It made the game fun again, and allowed them to keep the rulesets for old world content the same while drastically changing game mechanics inside of abyssea.

That being said. I would not want to see an exact duplicate, but something along the same lines of open world NM hunting via pop systems would be cool.

The dungeons are always cool as an additional thing to do by the way. They just need to expand into other areas.