You mean that big, slow tank that's totally not going to be within range, of a faction the republic tentatively isn't at war with?
I think the Thunders are more likely, given that yes, if a Capellan player doesn't have any of those he's in the wrong army.
At least in fluff, I've read instances of military ECM being visible on scanners ways off, so I suppose having it on all the time will give your position away; That said, if you use the Narc version, your ARAD missiles thrive on the very thing that'll disable the drone, so I see no issue there.
I mean, from the books it looks to me like this one is for clandestine operations and scouting, we probably shouldn't assume they'll be deployed where counters are expected. At least not in combat, that is.
... and now I wonder why the Republic hasn't developed an ERTAG. ;D