If they do orbits, they should be calculated as analytically as possible first, which would mean simplifying them, unless they have really good processing power to update all of those coordinates. Orbital errors also accumulate really fast.
Maybe you could do a system where you have an approximation to the n body problem where you calculate something’s trajectory based only on the dominant gravitational field. Or, if you had a binary star system you’d just do an elliptical orbit around the center of mass of the binary star system. That would be computationally cheap, since you’d literally just update the 3d coordinates as a function of time.
The only thing that this leaves out is things like lagrange points and transfer orbits.