That would be awesome, but I doubt Cassandra would care.
Vivienne has her status to keep in mind if she want to survive the Grand Game. That's limit her to human only to avoid scandals. Cassandra could have something similar with her being a noble of royal blood and all that, but we haven't seen any indication that she cares about her social standing unlike Vivienne.
If Vivienne is a LI I could definitely see her and Cullen being the race gated ones. Guess we will see.
Also I think no matter how you look at it a mage inquisitor is probably going to get some mixed feelings out of Cassandra whether it is based on her brother getting killed by mages or the mage-templar war that is going on.
The topic of Cassandra and the Trevalyan being able to relate in to each other when it comes to the fact that both seems to have abandoned their nobility is interesting. I wonder though, just how powerful is the Trevalyan family?