Not a Cass fan? 
Hmm...Not sure how to put it...Well let us just say religious girls and me do not end up getting along in the romantic department...
That and I almost always roleplay as a mage, so the idea of being in a meaningful relationship with someone whose job / purpose / role is to lock me up because it is for my own good is, repulsive.
Now others would tell you that this can work, this might work, bla bla bla, but I am not looking for unnecessary drama and baggage in a romantic relationship of any kind, even one in a game...
It is why my Wardens never had a thing for Leliana. It is why my female mage Wardens never had a thing for Cullen, to them he is a Templar that they have to tolerate and deal with. It is why my Hawkes never had a thing for Sebastian either.
So Cassandra, being a Seeker...Unless if she shows that she can get over the whole Right Hand thing, get over my Inquisitor's Dalish origins...If so then yeah, why not ?
It boils down to Josephine and Cassandra for me. For now, Josephine has a massive lead in that department.