For those that don't want to see there Warden again in a DLC, they could simply not buy "said" DLC. And for those that have a dead Warden, the story could still use "a" Warden to tell it, similar to how there's Shroad/Alistair/Loghain for that one mission. An since Bioware already invented the Orlesian Warden from Awakening/Witch Hunt, they could always use that character for those who killed their Warden. And for those who kept their Warden alive, they can finally get closure on that character's storyline. Eitherway, there's a Warden running around trying to stop the Calling that Bioware can tell a story with.
Voice wise, believe it or not Bioware already gave a voice to a Warden AND allowed us to choice which one we wanted way back in Origin, though that voice only said commands in combat. I picked Mark Meer's voice, so if they bring him and the other voices back for it, and allow me to pick, I'd be happy.
Personality wise, that can be somewhat solved:
"So Morrigan, what was the warden like?"
"Well... she/he was...."
a) A kind and diplomatic person
A person you couldn't take seriously. Always trying to say a joke.
c) A complete dick. Always angry, and trying to kill people with his murder knife.