Essentially, I wouldn't. Because each expansion is a continuation of the previous story, and even 1.0 players started ARR with their existing levels and EXP intact, it wasn't reset (thus there was a whole section of players who started ARR at level cap), so such an idea would completely invalidate that.

New players who want to skip ahead to the most recent expansion have the story skip items on the Online Store to use anyway, so such an idea is completely redundant.