I think the Wesley of season one could have maybe made a go of a relationship with Fred but she was busy surviving Pylea... thing is, Wesley was always a darker character than we initially see... he's a watcher, he's got a very dark relationship with his father (and probably his family) We see hints of it during Billy. I think that people pair the two of them together because they're both smart, but Wesley is book smart and Fred is just gifted... Fred is far and away the smartest person on the series... she might have more in common in terms of smarts with Willow (and maybe Oz - there's a reason the 'Microsoft' of the Buffyverse was looking to meet with both Willow and Oz). That said, Fred is eminently practical AEB her creativity with trap making in Billy, her survival in Pylea and the contraption she builds that kills demons... Same as Gunn, who makes his own weapons... They are survivors. Fred survived five years in hell. Wesley barely survived Sunnydale graduation!! Wesley was not initially good at fighting or much of anything practical... he's a very bookish kind of guy who would rather spend time with his head inside some complicated translation than go out and fight... he gets
competent at it, but it's not his nature. If you watch Fred fight, she's actually a natural. She's small and she's deceptively fragile, but she uses that.
I know opposites do attract... but similars stay together and build lives. (been married, divorced, married and widowed and married again) For people who are different to do well together, they must complement each other. I don't see it with Wes and Fred. They also have some of the same weaknesses (shy, awkward) -- probably why then never actually end up together.
You left out my all time favorite, Angel and Nina. Given another Season, I think that they would have really grown into a strong couple, especially if Nina had somehow learned to both control her changes AND stay in control when she did change. They could have made almost as good a fighting team as Buffy and Spike. Plus, the dynamic between a vampire and a werewolf would have been almost as interesting as that between a vampire and a Slayer.
I would love to have seen how they got around the curse (and Buffy's reaction if she found out, though I think that ship has long sailed). I don't think the curse would initially be a problem (I don't believe Angel was a monk) I think if they fell in love and were truly happy, though...
By the way... I really love Wesley... and I love writing him.
I love when people ship Graham with characters other than Riley. I used to read Xander/Graham fics in the past. I just love how fanfic writers shaped his character in the same way (kinda like Riley, but slightly less uptight).
I love Graham and wish he'd been a more major character. When I need to bring an initiative character, he's my go to guy. I have shipped him with Buffy. I think they are a fun match. Buffy is much more... intense even than I think Riley could handle... I think Graham would roll better with the punches. I don't think Buffy's in-chargeness would scare him as much.
I decided that someone like Faith needs a Riley in her life... someone who'll worship her, but also ground her... and she'll challenge him to let loose in a way Buffy really won't b/c she's too buttoned down.