Just to put my two cents in this conversation, the difference in NY and James, and MK and James is James is closer to BOTH Nadech and Yaya. They have an almost like family relationship. James look up to Nadech as an older brother, which makes Yaya as a sister-in-law. Whereas, with MK and James, James is only close to Kim in some extensions. James and Mark are still quite unfamiliar with one another. The bond between Nadech and James makes it hard for fans to look at James and Yaya as potential partners in real life, at least that's how I feel it. Even if one day NY's no longer together (which I highly doubt it), I can't see James with Yaya because of his relationship with Nadech. With James and Kim I can still have hope, because if anything ever to happen to MK (which I doubt it), I can be assured that it will not affect KimJa's relationship, which gives us KimJa's fans an opportunity to ship them for real. Does that make sense?
Another reason is James and Yaya have mutual feelings for each other, at least that's how I see it. Neither one likes each other romantically. With James and Kim, we at least can agree that James does indeed hover a little crush for Kim, even if Kim does not feel the same way.
With that being say, I have no problem shipping James and Yaya together onscreen. I would love to see them act together to be honest. I think they are physically compatible for one another. It's the same feeling I have for Kim and James Ji. I know James Ji is close to Mark, but when his lakorn with Kim comes out I can tell you I'll be shipping them like how I was shipping KimJa. Same with Mark and Yaya, I'm excited to see them in their upcoming lakorn.
We're not disrespecting MK's relationship, well I"m not. I'm very happy for Kim to be able to find someone she can be happy with. I think she glows when she's with Mark. She's obviously very happy at the moment and as a fan I'm happy for her. With all that MK has gone through, I truly hope they do end up together. I hope Mark truly treasure Kim because I feel like Kim has sacrificed a lot to be with him, and I hope he's graceful for the love she's given him.