Nth'ing for Nathaniel. I would die a happy woman if he were to be romanceable. And given the Warden's 5-30 year lifespan, and the fact that at the end of DA2 he's been a Warden for 8-9 years (if he lived) there's the potential for some awesomely heartbreaking drama with his Calling.
Also I know that Galyan/Cass was hinted at in the movie, but I'd really enjoy romancing Galyan. Unf. He's amusing, sweet, and with a kindness to him.
And I'd also love the Tevinter Magister that's been hinted at in the survey. I do love mage revolutionaries.
Cullen's psycho dialogue in DA:O was a major turn-off for me, added to the ending where he went crazy and slaughtered a bunch of innocent mage apprentices. No thank you.
Also I'd LOVE to see where a Sebastian rivalmance goes...

I know Hawke will only be returning as an NPC if at all, though. Give us a chance to REALLY rivalmance the prince in DA3.
I think what I'd really like in a male LI is confidence. That really drew me to Zev, and I liked his friendlier attitude in contrast to Fenris' aggressive bravado. I love Anders more than any male LI, but he's a very vulnerable man, and I don't need all of my favorite LIs to be clones of each other.
I think someone with a strong sense of honor, perhaps a warrior's self-control would be intriguing as well- a bit like Garrus, where he could be a steadfast friend and companion, but also a surprisingly wonderful romance.
Also nth'ing for dark hair- Al, Zev and Anders are blondies, Seb's a redhead, Fen might have been dark-haired at one time if his eyebrows are any indication, but we've yet to have a raven-haired male LI.
Of course most of the above come back to Nathaniel.