AAARGH the second patch broke the graphic from the Dawn Will Come scenes!!! My quizzy now wears plastic pants at these scenes ... Even after hotfix everything is fine except the pants colour & texture!!!!!
See, in MY mind, if he loved my Inquisitor he would want to do it himself rather than let someone else who didn't care for her do it. 
Well to me it feels like Connor's case is more like oddity. There is tons of abominations in the DA series but we just kill them without even having option to save people. Maybe there was something different about the Connor, most of abominations are transmutated but he wasn't. He was also able to break free at times, to me it seemed more like demon was controlling his mind but not fully possessed his body. So maybe there is different stages of possession.
I remember at Connor's case it was said that Connor gave himself to possession willingly and that's why he can be exorcized. Irving feeling deeply indebted for the Warden helped too...
I actually like the option to ask Cullen to... do what must be done if my magequisitor romancing him got possessed by a demon... It's heartbreaking & break her heart to see him suffer with this thought. But he's among the very few she can trust with this...