In a typical Modelica model, a component (like a planet) would know about and interact with other components via its connections, and each object is connected with a small number of "nearby" objects. For an orrery where each body interact with every other body, this is a poor fit.

What you can always do is to manually gather all relevant equations into one big model, and just connect it with visualization from the MultiBody library.

To get a fancier look of the bodies, you may use a CAD shape for visualization. Here is an example: http://community.wolfram.com/groups/-/m/t/345538