Generally I agree with a lot of the points you're making in your post, with the exception of what I quoted here.
If a movie was going to limit itself solely to the characterization we see on page, you might have an argument. I mean, literary analysis being what it is, it'd still be highly, highly subjective, but I could see your point. But a movie isn't limited by the source material. They could, can, and have, added various little tweaks and adjustments to characters to round out the narrative. For example, to my limited knowledge we've never seen Tony Stark pine for a kid of his own, but that's what we got in Infinity War and that informed a lot of Tony's arc in the film, while also driving the gut punch of Parker's Snapping home.
I think Rich and Sam both have enough characterization in the comics to serve as a solid foundation, and then whatever is missing can easily be filled in by the script.
I do like the idea of a buddy cop movie. It's a different kind of genre for Marvel Studios and it gives all Nova fans what they want. But I dont think it's necessarily the "better" or "must-do" option overall, even if it does have its strong points and arguably better optics (at least in some ways) than just doing one Nova or the other.