Worf and Tasha.
Tasha was supposed to be the strong female in TNG and they never really wrote her that way. Every time they showed her as strong they immediately turned her into a victim. They even give us a hint in Skin of Evil that the writers wanted to pair her with Worf. That would have been great because she would have been a worthy rival, and he would have brought out more of her strong woman side.
Kim and Seven might have been funny. And I think there's a peculiar logic to it. Kim is the most non-threatening heterosexual male in the universe, and Seven is a dominating mother figure for him.
Also Riker/Ro would have been fun for an 'occasional fling' sort of situation, because then Ro would have been the dominating one in the relationship, and we could see Riker get treated the way he treats other women.