We now need run some additional nodes. First of all, we run Gazebo, and (if we want, I currently commented it out) RViz. Then we spawn robots. We create Localization nodes, as well as Path Planner nodes. And Coordinator node. And so on. So let's take a look at a new multi_simulation_launch.py:
Note that any software developer will immediately suggest to combine some (or all) robot-related classes initialization... Ideally, to move the "for all robots" cycle into the Coordinator's code. I might address the issue later.