Well, dealing with eccentricity needs simulation not only calculation, so it's very hard to do. To be honest, this planner does very simple calculation based on Euclidean geometry, in short, only handles circles, points and lines in a certain moment. As you say, I think more complicated and time-related calculation is necessary for elliptic orbits. I don't aim for create an orbit simulator in this moment, sorry. P.S. After thinking about the third Delta-V view, I realized it can be possible to deal with inclination as long as all satellites are in the single orbit.