Just a little fluff. People always start Destiel with a kiss. I'm gonna go with a dance. Ianto and Jack dancing came to mind, and I thought, yeah.
Because most fanfics are like "well, that escalated quickly" and even after a few seasons (I'm just on Season 6) Cas and Dean still have an interesting relationship, strained by duties. Duties they put on themselves, but still. Dean dealing with souless Sam and Castiel dealing with putting order to his home.
As far as I can tell, there is that profound bond, but while I count Sam mentioning Dean overcompensating and the "Last time someone looked at me like that, I got laid" comment from Dean when Cass was seething with loathing at him, I really don't see Dean admitting to anyone, especially himself, that he feels anything sexual for Cass.
(And I will spell it Cass. The captioning has it like that and Misha himself insists it's spelled that way and showing the script proving the spelling.)
In any case, I see where the writers have at least left it OPEN. They may or may not do a romance there, but there it is.
Also believing myself to be poly, I see no reason why they can't be together, even without sex, at least at first. I'm thinking a Shamy sort of situation.
So I'm going to work them into it slowly. Right now, where I am with the series, Cass was snarky about Dean selfishly insisting he work on Sam's issue... even in the mist of a civil war, however, later that same episode, Cass wistfully stated he'd rather be there on Earth.
Dean has used "friend" for Cass, so that's the state where I'll work up to this first bout of writing.