Now hear me out on this, but he could no role since he disappeared..
And why did he/she disappear? Hawke potentially has a hugely powerful bond with his friends and I doubt Varric wouldn't want to find Hawke. Furthermore it's very suspicious for the Warden and Hawke to vanish no matter what. Something happened and hopefully DAI addresses this.
Furthermore nothing is stopping Bioware from having a system like ME series on the PS3 where you could choose how big events occurred in past games, without importing. Heck, they could even allow the player the option, later on before meeting Hawke and/or the Warden, to choose how they look in DAI.
Not addressing them or even showing them during this huge event or why they vanished would be highly disappointing and hurts the narrative due to how important these characters are to DA.