Simple Orbital Mechanics Simulator please

A tool which I wish existed: Simple Orbital Mechanics Simulator

Features:

-Importing custom planetary systems
-Running either N-body or Keplerian orbits
-A spacecraft which can be teleported into orbit, and is capable of performing single impulses of thrust using KSP's maneuver node system. The spacecraft can be given infinite fuel or a limited amount of Delta-V.
-Porkchop Plot (i.e., KSP Transfer Window Planner) to see when transfer windows are and what the delta-v to transfer is.
-Output of Hohmann Transfer Delta-V between any bodies.
-Running either N-body or Patched Conic orbital trajectories for spacecrafts.