Dungeons - Replacing members

Nothing is more frustrating, especially as a DPS who have considerably longer queues than tanks or healers, than joining a group and then having your tank or healer leave and then waiting an additional amount of unknown time to replace that role with an individual who just so happens to have the in-progress dungeon option selected in their Duty Finder (most dont). I would like to propose a solution:

- In the event that a party member leaves allow the other participants to change class to the missing role while still earning XP as the class for which they queued. For example, you queue into a dungeon as a SAM and your healer leaves halfway through. You role swap to your healer to decrease the amount of waiting and allow your party to fill so that you may continue to progress. For the rest of the dungeon the game continues to identify you as your SAM and you earn XP for that job/class.

You could restrict this option only to people switching into Tank/Healer role to avoid trolling however I don't think there would really be much need for that given that if a person queued as a Tank or Healer they are prepared to play that role. In the event that a DPS leaves those two roles would have very little incentive to switch as it would only increase the amount of time they would have to wait to continue earning XP for that class.