Training raid mode , where you can kill the boss multiple times, can resurrect the players mid fight, and not get one shotted from every mechanic. Of course this is for training purpose only so rewards is out of the question. That would be perfect for every beginner stepping for the first time in the raids, having a chance to experience what is a raid, teaming up with 10 players, trying the mechanics, their dps, rotations, etc. Also will be great for testing new players before adding them to a static group.
This would be cool to be accessible even after the boss kill on empty wing.