No way with radio but with action, as they say all.
I have done an "Action Command Engine" it works in MP. You can dowload it here :
http://www.ofpec.com/yabbse/index.php?board=7;action=display;threadid=2095Grosso modo you do this :
Detect players in the init script, install the action detection script (cause you need to detect if players are in or out vehicle)
After it's "simple" cause actions are give to the right player.
If you want a pure script you can test who call the action (cause if you are near an object with action you can call it ) with param return with action key (_This select 1 contain the caller object)
I forget something BenReeper in is mod
Battle War use a mirror radio button of the action keys, so I think it's possible with radio script whith a player detection for example...
PS ACE is for multi-squad MP, I have done very light versions of it, you can ask them in the CoC forum...