-Stormblood spoilers-
Many allies who have died (for now) had quests in which we pay tribute to them: Moenbryda, Haurchefant, Ysayle, Louisoix/Nael/Bahamut's children, Minfilia/Warburton, Tesleen... even Nidhogg had his tribute quest. I would ask for one focused in Papalymo, a character who has been with us since 1.0.
I understand, after Papalymo's death, Lyse and the Scions were suddenly too busy with the Ala Mhigan Resistance, and just after that, the Scions' departure to the First. Now that both situations have been solved or controlled, I think this would be the perfect moment.
Another character I think deserves a tribute quest may be Tsuyu (not Yotsuyu, the good one).