Can I build a solar system simulator with this? Looking for calculating the absolute positions of planets and moons with the sun at 0,0,0 given a datetime. Kepler calculations for planets, moons etc would be fine, as long as I can insert arbitrary objects and calculate their trajectory using gravity. Can this project do that?

We already have the possibility to get positions of celestial bodies with very high precision via JPL ephemerides but you would have to write and integrate your force model yourself.