As patient and dedicated as Shera is with Cid, I'm pretty sure she loves him. He eventually marries her and even if Cid isn't the lovey-dovey type, (he wouldn't be our Cid if he was), he has his own ways of showing affection for Shera.
I'm very open when it comes to pairings, and tend to like odd couples. It is a rare occasion when I like a canon couple, as I usually either dislike them, or most often I am indifferent to them.
I really can't think of pairing up Shera with anyone else, it just doesn't feel like it fits. Believe me, just because a pairing is canon is never a good reason for me to support it, in fact, if I like a different couple I'll stick with the one I like regardless of what's canon and what isn't. The pairing of Cid and Shera is exception because it fits very well in its own special way, making it one of the few canon couples I like.
This couple isn't really all that lovey-dovey, which is actually a good thing in my opinion, because I have always been bored by the perfect little couples that are all lovey all the time. Cid and Shera have a special understanding and loyalty, without excessive romantic mushiness.
Other possibilities for Shera pairings? In the world of fanfiction anything is possible, and if it's well written it might work. But in the end, I still like CidxShera best.