recommendation for a programable FPS game for training forces [closed]

I wish to develop a training simulator for army ground forces.

Basic concept is that they can save lots of training time and budget by going through a simulator phase before the physical war-training, explicitly, learning:

  • How to cooperate with one another and improve team work
  • Learn the basics of their weapons capabilities
  • Learn the territory of interest
  • Develop and practice different tactics

All this at a low cost relative to only physical training.

Where should I start? what platforms are available that can be used for effective war-training and can be easily adapted to new maps/fighting territories and warfare equipment?