This "non-determinism" argument was also levelled against Ethernet back in the 1980s, when Token-Ring was still considered a serious contender and certain large manufacturing companies were trying to push something called "Manufacturing Automation Protocol" (MAP) for use in real-time situations on factory floors.

All that is forgotten history now. Supposedly "non-deterministic" protocols like Ethernet and TCP/IP won out through sheer cost-effectiveness.

And don't forget, those were the days of the Cold War, when the military-industrial complex had access to even more taxpayer money than they do now. So the pressure on the purse-strings is even tighter. So the only option left for many projects is either heavy use of COTS (Commercial Off-The-Shelf) technology, or complete cancellation.

Would be nice to play a quick round before the server blows up in an insurgent tank (in real life, I mean).

I can see it now "Would you guys stop shooting the insurgents, every time you shoot I get huge packet loss"

Bullets are deterministic, Internet Protocol is not. They should use a deterministic protocol like MIL-STD-1553 - although the cabling might be a bit inconvenient.