Straker has dry wit, so does Ginny. I think that is why it worked so well. They understand each other.
Ed very seldom let us see that side of his personality, ocasionally, with his interaction with Alec, and on the ride to the studio, with Ginny. That was an aspect you captured well in
Fallen Heroes. I tend to believe that is how the writer's would have portrayed them had UFO gone a second season. If they were smart, they would have left the UST in the mix.
I'm not sure how it would go with Nina. I think there was something there, but as I recall you mentioned somewhere that most of the heat was on Nina's side. I agree. The comment that Straker makes in the hospital about "the things we never say," makes me wonder, however, if he was thinking about it. :

The only episode where they interacted closely was
Subsmash, a good excuse to review that one again.
The only way to tell might be to put them on paper and let them have at it.

We might all be surprised. :