Everyone (romanceable) is bisexual. That is the only real must-have on my personal Wish List. I loved everything about the romances and dialogues in DA:O, just as much as I loved everything about the romances and dialogues in DA2. These aspects in both games were great to me, even if they both do slightly differ in various ways. Ways in which we are discussing above, I notice. If a compromise/merging of the two can be found, I'll still be quite happy.
I did enjoy more companion questlines for each character. It provided a great opportunity for character portraiting and depth, as well as good opportunities for interpersonal drama (moral disagreements, betrayals, arguments, siding with a companion's choice even if it was a Bad Thing -- a la the mirror and Merrill's blood magicy ways). Maybe seeing the romance portion play out a bit more in those scenarios? Or holding a bit more weight in certain dialogue/decisions.
Or perhaps what I'm thinking about is more general. I'd like to see your romanceable companion show more concern and worry for the PC's well-being. If ambushed by blood mages in a quest, the follow-up cinematic with your LI in the party would be nice if they got to supercede the questline dialogue/banters by asking if you're okay/injured. Deathtraps and lethal interactions happen every day in a Hero's life, I know, but having some of the more momentus occassions, the bigger threats, come with some dash of affection/acknowledgement on the side would be nice. One thing I loved most about DA2 was how it utilized companions' skills and abilities and special dialogue moments in conversations where appropriate. Like a mage friend stepping in to help when the (non-mage) PC is getting bamboozled by blood magic mind-control, or Aveline using her power as a Captain and her authority to control a situation/solve a scenario, etc etc. Awesome little things.
Aveline, in general, is a great example of a character progressing through her own goals and ambitions and making her own life choices, while still being a relevant companion in the PC's overall quest, and utilizing her position and authority where appropriate. It never felt like her agency or capabilities had to be toned down in order to not outshine the PC. I rather all the companions (particularly the romanceable ones) come with such agency and equal opportunity in the game, being on somewhat equal footing as the PC, rather than just 'misfit tagalongs to the Messiah Savior that is great at all things all the time.'