I did not do this, though I love-- OP-- that you thought of this, and yeah, I wish there was an in-game reward for doing so.
I did continue doing all the Dalish tasks, even after I'd gotten enough favor to recruit the warrior. I wish there was some note of this, too-- because my Inquisitor (and my personal feelings, in this case), though human, strongly supports the elves and the Dalish clans, and I wish this was noted.
The only real opportunity to help elves and make a (significant) difference in the game is with Briala, and that was too high a cost, in my opinion-- Briala was very sympathetic, but having Gaspard executed and keeping Briala's machinations from Celene seemed too high a price. Along with the fact that (those who read Masked Empire tell me) that C & B's relationship was not great to begin with, I just didn't feel comfortable "reuniting them," especailly when Gaspard is summarily executed for doing pretty much the same thing as everyone else. I digress, however...
Great thread! Cheers.