OK, I'm thinking out loud (at least, I think I‘ve thought about this):
Remote detonators for satchel charges have a finite range, but I've not experienced a maximum range with unit radios. IF they were limited there might be some possibility of reducing the range to simulate voice contact, but it seems unlikely. The scripting required to disable/avoid the radio comms and then to substitute a [possibly horribly complex] alternative seems, er, possibly horribly complex.
Th best I can offer at the moment is to float a couple of off-the-cuff concepts . . .
Idea 1:
?(Ready unit && unit Distance Leader unit > voicerange): unit stop true
?(unit Distance Leader unit < voicerange): unit stop false
?(Not Ready unit < voicerange): Leader unit Say "something audible so he can be detected"
Pros:
Still uses the game's interface, but its effects are overridden.
Units should complete tasks beyond voicerange before being stopped.
Within voicerange, ‘radio' commands should be executed.
Should work for AI leaders and units.
Cons:
First guess is a script per unit with the two conditions.
voicerange needs to be great enough to allow groups to move with leader in formation, otherwise units will get left behind.
It may not work.
Idea 2:
Commander is on his own and bimbles around with a big trigger attached around him (or maybe SetPos'd out in front of him so there's a bit of selectivity, he'd have to face the unit(s).
Friendly units in his trigger list Join him.
Commander (now Leader) can issue ‘radio' commands as we all know and love, and units should execute them.
Outside his trigger, units Join GrpNull (or their original group could be archived and retrieved, I suppose)
Pros:
Not much (maybe ‘no') scripting.
Be your own Field Marshal - control anyone and everyone.
Cons:
New minions may run after you rather than carrying on with what they were doing.
Don't trust that GrpNull much - will orders continue to be executed after the Join GrpNull?
This may not work either.
Any thoughts on the prcticality of these,anyone?