I imagine a strict ECM jammer would just add 1d6 as a skill penalty against guided missiles and any other attacks requiring a lock-on.
Being a device, an interference module would require an action to activate. It's not a half-mind, it's just a button.
I think worrying about communications and whether or not units can "talk to each other" is pretty un-brikwars. Minifigs instinctively know when blood is being spilled, and where it's about to flow. Minifigs magically know whats going on in the battlefield at all times because the player knows what's happening at all times. This is why I chose for it to interrupt combined attacks - radio communications or shouting or whatever would be the standard way that minifigs would coordinate a combined attack. The idea came from the game The Creature that Ate Sheboygan, although in that game, being radioactive meant that NO combined attacks could be made at all against the target (unless they were in the same square but Brikwars don't work that way).
If there were some cool way to mess with combined attacks and radio communications, I'd go more along that route than the efficient transfer of orders. I'm not going to tell you how to play the game and what is and isn't fun, so feel free to work the game that way if you like it.