Messing with the orbits of planets.

I dont even know if this is possible but would it even be possible to add orbital physics? I mean, if I ram a moon into a planet the planet is going to speed up its rotation and or get knocked out of its original orbit. If this feature is added, whole planets could be crashing into each other and not just asteroids.... Not to mention the planets crashing into suns...

Oh come on, another thread on this?

Try here
Specifically, this topic: Planetary / Orbital body Dynamics.
And even more specific, the last post, which already linked to another topic (which even has a poll, that's how old it is).