Let's see my official feeling on pairings in FMA. Well I'm all for the Win Ed pairing. I tend to think of the pair of them like a love/hate kinda thing. I can't imagine that the two of them would ever be lovey dovey, I can see them butting heads, I can see her pulling out the chainsaw every now and then. But that's just their characters. The pair of them like to be in charge of everything, so having them be in a relationship other than just friends is gonna be one hell of a growth spurt(pardon the pun) for old Ed and Win.
Now the Roy Riza pairing is pretty much stamped on every page, how anyone could miss it is beyond me. I think I understand why it is that they tend to keep this thing quiet. The biggest reason is that Roy is Riza's superior officer, bascially if they ever did get involved in the open they would both be up for a pair of court martials. Which I guess why he enjoys it so much, Roy strikes me as the kind of guy that doesn't go for the easy relationship(though he does enjoy them...). Riza also strikes me as the kind of woman, who does know that she's in love with him, but is also driven to see that he gets his dream.

Which basically is my way of saying I'm all for the pairing, but I don't think it's gonna go any further until he has the power to pardon himself. In other words, when he becomes fuhrer(I can't for the life of me figure out how to spell that.).
As for the Win Al pairing, I'd really have to stretch my imagination on that one. I can see them as really good friends, but anything more than that would be on the far fetched realm of possiblity. Especially considering I don't think Al has ever hinted at the possibility of him liking her as more than a friend. To me it seems as if Al sees Win as a big sister or this cousin that comes over all the time. Anyways...I just don't see it happening.
All this being said, I'm fairly certain someone will disagree with me. As for the yaoi pairings...I have only one reaction to that. Ewww.... To me that is really stretching it. I think I shall stop here for now.