Oh man, I totally see Fenris as the first category. He's a warrior who's nothing if not fully committed to his own moral compass, and virtuous to the extent that he wants to see evil punished (that guy in the cave killing elf girls) and chaos controlled (mages presided over by the templars) and the vulnerable protected (he bristles at Orana being a servant). He's never had a prior love interest so we can't even call his *potential* fling with Isabella promiscuous, and is a more than capable warrior, and bi. He gets a lot of flack for the haircut, being an elf, and not having a sunny disposition ala Alistair, but he fits your description to a T in my eyes.
Fenris is more a Knight in Sour Armor than he is a Knight in Shining Armor. I agree that he fits the description very well, but he's been jaded by the world, is dry/sarcastic/bitter, and has had that rosy optimism all but smothered. He's far more ends justify the means and willing to work outside the law to bring justice, even deliver justice by his own hands. You can compare him to Aveline, who will pass Fenris information about slavers so he can disappear them but won't break the law to do it herself. (They share a banter about it late in the Third Act if they're both in the party.) Fenris has a justifiable mistrust of authority and while he is very noble, he is also very brutal.
I'll just add another voice for really like to see an optimist Alistair type gay knight, particularly one a little like George R.R. Martin's Loras Tyrell, the Knight of Flowers except without the Martin twists. A powerful noble and expert warrior, possibly well-renowned struggling between a desire to pursue the romance he wants but also his responsibility to his house. I know that sort of Dorian's plotline, but I personally think it plays out better in the context of a nobility structure we already know and relate to (Fereldan, Kirkwall, Orlais). Tevinter fits into the "obviously evil"/enemy nation category and Dorian's story seems to be "I would be forced into" as opposed to "I am torn between my heart and duty". It's a story built around love, compassion, and filial duty with the Knight's family being similar to say the Couslands. Alistairesque with Dorian's basic skeletal plot outline. Run the plot like any standard heterosexual star crossed lovers plot, Knight and Lover, Alistair and Warden, whichever and just go with it.
It'd give us a chance to get a good look at (Orlais, Fereldan) politics between the nobility which we haven't really had before. Alistair was a prince, but he wasn't raised in the court or have a noble's understanding of Fereldan politics. He was essentially a commoner. Sebastian was a prince and the closest we've had to a noble party member, but that role was really usurped by his religious beliefs and while those were important perspective in DA2, didn't really help us to understand the higher workings of Kirkwall. Cassandra is formerly a noble, I think, but again she's in a similar position to Sebastian and Alistair as their position is mainly as representatives of Group X (Warden, Chantry) and not as a spokesperson for the noble class or greater world politics. So far, Dragon Age has treated it's noble class as foppish, silly, evil, largely forgettable rich people and it'd be nice to see that change. (Or at least explain why they're still largely in charge.)