Okay. Ideas that got a spark out of me. Ones I marked with ***** are ones where I have a plot I created a while ago that lines up with what you said almost exactly.
Warrior x Mage *****
God x Mortal (If I could play the god)
Detective x “Bad Guy” *****
Alien x Human
Death x Mortal (If I could play death)
Dark Half x Light Half (For some reason, my brain jumped to the idea of dissociative identity disorder. Which would make a very, very odd plot. But potentially interesting)
Accidental Hero x Fated Protector *****
Prince/King x Vampire (IICB the vampire)
In a land where people abandon their children to be raised in the wild as a natural part of their lives, a pair of twins are separated at birth, each selected by a different monster to be raise. They grow up, raised by these beasts less than a mile apart, separated by a wide river. One day one of the twins rescues the other from the river after a storm and they decide to travel together, with their beloved monsters at their sides to aid them in their journeys.
A creature is lurking through the streets at night, killing at random. A seasoned cop is hot on it's trail having tracked it across country. A talented young officer is assigned to the case, their keen eyes and powers of observation helping to point the cops in the right direction. The veterann at first takes issue with being assigned a greeny, but the vet soon starts to realize that it's more than natural talent guiding this young one. The newbie has a gift, and it's time to give it a workout. (IICB the newbie)
They have been hunted to near extinction. Where once they lived, in harmony with the local human tribes, they now must hide and scavenge where they can. As some of the last remaining members of the monster tribe, the small group of creatures must find a place to call their own. Lead by a strong fighter they pass through the human lands. There they come across a human who sympathizes with their plight and decides to travel with them, aiding them when and where possible. But the queen's royal hunters have been dispatched, and it's only a matter of time before they find the wayward band.
I'm sure there are others, but I ran out of reading patience.
But I get your point all the same. So long as you keep a generally consistent geography with reality (not putting Chicago next to an ocean, putting New York City on top of the tallest mountain in the country, etc) I wouldn't mind. Just don't necessarily expect me to do the same.