Ah, the great pairings debate.
Logically speaking, it's theoretically possible to pair anyone together.
It just takes skill to create a scenario that makes the development believable and not requiring the audience to have to enter a state of suspension of disbelief. XDDD
Personally, since I'm such a fervent fan of Aichan, all I really need or want to see is a detailed or at least, decent portrayal of her.
I don't mind reading anything that has her in one of the pairings, as long as it's done well. And by done well...let's just say I'm not a big fan of the whole "omg I love you let's have sex!" way of doing things. >_> XDDD Which is why I generally am not too enthused about the perv section except for a few gems there.
Favored pairings though...well, TakaGaki is good for fluff. Most of my early Sandbox entries were TakaGaki, because I felt like writing cutesy stories and so, there they were! Lol. Then I moved on to ReinAi, because Saikami asked for a ReinAi fic for her birthday and I did it...and discovered that hey, the dynamic is fun!
Besides, Reina is my second favorite member so that helps. Lol.
Other pairings that I like that doesn't involve Ai would be Ishiyoshi and GAM. I'm pretty flexible about pairing possibilities, although I tend to favor those where I can feel the strong bonds of friendship underlying it.
I also like pairings where a certain amount of mutual teasing is involved. Verbal sparring is always entertaining, and I enjoy both reading and writing it.
Basically what I like to see in a relationship is trust, be it already established or still in the budding stages. Lust is never enough on its own. It can be a good starting point (or bad, depending on how you look at it), but I generally prefer that there be more depth in a relationship.
I think I'm rambling on for too long.
But that's how I see pairings. And by pairings, I don't necessarily always mean romantic! I like me a good rivalry, or just best friends as well. There are always so many options to pick from. Yup. ^_^