A radio man was trialed early on in Rising Storm development, but I believe it was removed due to problems with how roles are set up in RO2/RS (there needs to be an "equivalent" role on the other team. For example japanese knee mortar to US flamethrower).
why not a japanese signalman with "signal" flags?
have him not actually give flag messages, but same use (also could be a telephone man. (just assume wherever he is a phone line runs)