Infinite ups to Ken and Gaby getting together, those crazy kids have been through so much together.
I think Jacob and Kasumi could work. I'm for it. Thief and Corsair, go fall in love.
I think Miranda and Kaidan could work, and there would be fireworks. I'm for it. Miranda has to be an L2 herself, right? And he's a genuinely good man, something she's never really seen before.
I don't think there's really anyone for Joker, though they could add someone for him. Maybe if EDI gets an Overlord-style hybrid consciousness, and a nifty android body (that looks like Tricia Helfer). Or Kelly.
Jack is a mess, I don't know who could really sort her baggage and not somehow die in the process other than Shepard. Maybe a new character? Maybe a krogan? I got nothin'.
Dr. Chakwas is a confirmed spinster, and more power to her. Same goes for Samara. These ladies don't need no love from no mens/womens/aliens.
Mordin is a salarian, and they don't cotton to that messy hormonal crap, bless 'em.
Thane is also pretty resolutely solitary if Shepard doesn't get inside his head. I can't imagine anyone else on the Normandy having that affect on Thane.
Tali will fall into derpy lovegoo at the drop of a helmet, so yeah, marry her off to the nearest volus. Actually I would love to see her end up with Kal'Reeger, because Reeger seems to be a rather unique specimen: an actual quarian badass.
Garrus is a gruff old git with a chip on his shoulder and no real place in society except on the Normandy. Would he 'go alien' with anyone but Shepard? Dunno, but I bet an asari could turn his head, though probably not Liara or Samara. Aria maybe.
Zaeed is literally insane with rage. He isn't anywhere near in the right headspace to have feelings for someone. I kinda get a vibe from Z that he likes his own kind, so maybe Big Ben sniper dude?
Grunt is a krogan. I got nothin'.
Ashley is a big question mark. The only guy besides ManShep that I could ever see her with is Kaidan, and we all know that ain't gonna happen.