According to the definition in RFC 3489, NAT types are divided into four types: full cone, restricted cone, port restricted cone, symmetric
How to implement fullcone on ROS
It might be possible to mimic that behaviour using a src-nat rule if the game always uses a single UDP port for peer-to-peer communication:
/ip firewall nat
add chain=srcnat protocol=udp dst-port=1024-65535 src-address=the.ip.of.the.console action=src-nat to-addresses=the.wan.ip.address to-ports=12345
If you have more than one gaming console, you have to use a different external port (to-ports) for each of them.