my suggestion is
global,side,command chatting are similar to traditional system.(or give random channel,if ability to tap by taking enemy's radio,and person who get enemy's radio should know only group channel,or cant tap side,command channel at all)
but,at least,group chatting needs numbered channel and player can change their radio channel,or custom channel that players want to be set in isolation from group channel is needed.
and,coop mission there is only one squad dosen't need to set channel at all,just play like traditional system
(especially good for people playing domination as rescue ops,pilot,people playing gang on Altis Life,more secretly,because they are not in group,maybe? good to king of the hill).

and sorry for my bad english