Also what is the use of the ecm on clearly visual range. The effect of weapons (for example multi-part turrets) deliberately firing off their target even at point blank range because of ECM/ECCM values would be quite sight also. For longer range it might be nice but then again we already have the $fof available.
You do have the lead indicator? Not that I am suggesting that ECM should have any effect on fighters (other than perhaps secondary lock difficulties), nor should it even be on fighters (we have stealth allready). But the lead indicator is the most obvious thing in game indicating that there is a mess of electronics constantly "observing" your target, and likely assiting in target aquisation and tracking. Automated turrets should be voulnerable to any kind of ECM. Should the turrets in FS be controlled by real person, the gunner is still much depended on the information that electronic targetting systems supply him. Hence ECM would work in both cases.
But! Because of what Wanderer said the ECM would not be effective forever. Even the simpliest computer (in FS universe) or gunner should be able to realize that the shots are missing to the left and adust targetting to the right in order to hit. Thus negating the ECM effect.
Also. ECM in a ship as big as Colossus, for example, wouldn't really do much good. It's a big ship you could hit no matter what.
And. ECM in small craft like fighter is dead weight. It's small and agile and nothing ever really hits it anyway.
The biggest use would be for cruisers and corvettes. Does it make much differenve when SRed misses the Fenris? I think so.