Main Question or Discussion Point
What does it mean for an orbit to have a negative inclination? is it equivalent to an orbit with the same positive inclination but a shift in the node \Omega by \pi ?
For the situation you describe (working with small inclination changes near zero inclination) I could see it would be nice if Omega (longitue of the ascending node) do not "flip around" 180 degree just because there is a small change, but that would still be an unconventional way to represent orbital elements. For instance, when giving orbital elements like the two-line elements for earth satellites there are by definition never any negative inclinations, so if you were to see such a set with negative inclination you obviously have to question what that means.You would need negative inclination in order to do average cumulative changes.