To kick off this category, I would like to start a collection of cool existing ros projects/packages in this area.
The ones I know are:
Full Multi agents framework including MA-navigation and order (task) planner including rviz plugin and everything https://wiki.ros.org/tuw_multi_robot
A fleet manager to rule them all https://github.com/osrf/rmf_core
A fleet manager for the one above if you have none https://github.com/osrf/free_fleet