Inbound port access for eSports games in a K12 setting?

Several of our districts are moving forward with eSports leagues, playing LoL, overwatch, etc.

The NASEF IT guide mentions several ports to "forward" for best gameplay. The guide for overwatch mentions several tcp and udp ports to have "open."

Outbound ports are no problem--they are open already.

But inbound/forwarded ports--how could that work with more than one player behind a single public IP?

We do have the IP space to give each league its own public /26 or whatever...but something tells me I'm missing something, and it doesn't have to come to that. I don't play any of these games so I'm not familiar with their network architecture.