I just finished KH3 and learned about the Riku/Namine hype, and here's what I think about the this ship.
I'm naturally a very romantic person at heart, and I always look for shipping potential even if it's not the genre of what I'm watching/playing/reading. I think Riku and Namine would be great together and so super cute.
From a purely fandom fantasy perspective Riku deciding to keep his eye on Namine for the sake of Repliku is actually a very good premise for a romance story. He at first does it out of his loyal heart to Repliku but finds the more time he spends with Namine, the more of a bond they share. They have some similarities in their lives that could bring them closer for sure. Namine on the other hand would take some time to adapt to the real world and even having friends at all, but Riku's strong, reliable presence and bravery would be a great support that she eventually finds herself drawn to more and more.
This would be a great fanfic.
But, I don't believe it would ever happen in the games. That kind of stuff just doesn't happen. What do y'all think?