FFXI had this, it was called super jump, the dragoon essentially left the field and lost all aggro, the trade off being they were stuck in limbo for a few seconds.

But SE already shut down the idea of giving drg any kind of invincible. People used to complain that DRG should be invincible during jump because the animation lock was leading to a lot of deaths and was the origin of lolDRG. But SE said this would be unfair to other dps who have to actually do mechanics (then gave ninja perfect dodge).