These points have been discussed many times during EA. I think the issue with Origins companions is firstly that they have never been a part of previous BG games; so while there were always regenerated characters to use, we got to decide the personality and background of these characters. They were a blank slate in many respects. That is not the case with the Origins companions who have very defined personalities. I always found it a strange concept that you will be able to take someone like Astarion and role-play him as a 'good' character when that seems to go counter to his very being.
The other main issue is that the custom characters experience is lacking in comparison to using an Origins character, as was apparently the case with DOS2. Larian have promised to rectify this but then they promised some other things too which have not been forthcoming.
