What is the giant floating structure [in the middle of the tank map]?
SBo
In terms of why it's there, it's purely just so that people can easily see where the middle of the map is. Some of these maps are sizable.
Duncan BuntingLead Gameplay Programmer, Arena Commander Feature Team
We have plans for it.
starfarer.space · Star Citizen Live Gamedev: Arena Commander 3.20