I would love having my HoF back, but I'm terrified what Bioware would do with her voice and personalities. I would kill to have line dialogue choices again instead of the wheel. I felt like I could actually create a real personality instead of falling into nice, funny, or aggressive. Honestly, as much as I want her back, I think they are better off giving us one last good-bye mission in order to keep the HoF from being given the "Hawke in DAI" treatment.
I posted this in another topic, but I feel that it is incredibly relevant here:
Have a mission where the DA4 Protagonist goes to help the Warden that is trying to cure the calling. If your HoF is dead it's a Stroud-type replacement, the HoF's protegee perhaps? You don't actually make it in time to help so you have a badass fighting/puzzle mission where you get info on the Calling and curing it. At the end of the mission you get a cutscene of the HoF/Warden doing the thing to stop the calling. You can't actually have a conversation, just watching, maybe yelling things at the Warden. Then the HoF/Warden will cure the Calling and die, cure it and survive, not cure it, etc, this can be a set event or an event based on your choices.
And because people love the LI scene's (myself included), have an LI scene either prior to the cure attempt or after it.
Bippy bobbity boom, a mission that Bioware can't screw up with dialogue that doesn't fit the HoF's personality or a voice that doesn't match everyone's HoF and we get an answer to if it's possible to cure the calling.