The following are other efforts in creating simulators that can be useful.
The most advanced robotics simulator and it's open-sourced. Optimized for FRC simulations, this one is most likelly to be the de-facto standard of FTC once someone decides to mod it for FTC use. They do have a Velocity-Vortex field, you can import robots from Autodesk and a whole bunch of other features. If you're looking to help the FTC community by suppporting a simulator, I recommend putting your efforts into this one.
This one appears to be abondonned, but if you want to contact the authors you may want to use this as a starting point.
A unity project that the authors may donate to you if you ask. Also a good starting point.
Another FRC simulator.