We have had options to kill or destroy lives of some companions, but not everyone. Dorian with Solas is only one's you can even punch in whole franchise this far so I think you can be very dickish to those two especially in DAI when compared to others. I don't see why we should have option to kill or destroy Dorian's life particularly.
and almost every companions and now advisors what lives cannot be affected(only do good or more good but never bad things) by us and they are not a godlike(Solas/Morrigan) creatures is Dorian, Sera, Josephine, Lelianna, Isabella, Tallis. Traynor, Cortez. and others like them..now we would have Maevaris in DA4(and Charter who would replace Lelianna) and some new ones in ME
Cos he is Tevinter mage apostage and even if someone does not want to execute such as other Tevinters, so for mages and tevinter supporters they learn that he have a position against Tevinter, he is potential enemy of Templars and Mages/Tevinter supporters
and remember we can have a alliance with Tevinter and Archon in DA3
And we could cut his life so he would not become Magister, never have a seat in Senat, not become "opposition" with connection with Inquisition via Maevaris, we would not deal with him anymore if we have a choice and not let him become who he is become, we even could support and not support Calpernia but never have a choice with Dorian
he was originally not have any value for us, only temporaly and minor in mages quest with time breaking, so there is no point of why he is special while Bull and Blackwall and some characters in game is not
if he was stay as he was without becoming a magister who he should not be, and he was not become one without Inquisiton support, it was not really matter if he was die or not, but death is 90% save from characters appear
And now this "untouchable" will become our forced advisor/companion with Maevaris, i will not be surprised than Maevaris or Dorian will be Archon candidates and they as someone said would be "placed on a pedestal" and treated like special one above others