Allowing ACS Defend on anyone would permit to take even greater advantages of sensor phalanx by scanning potential targets and intercepting attacking fleets. The battles would only be dishonorable for the ACS Defender if combined military points exceed the threshold (as it should always in my opinion)

Time constraints, Recyclers speed & SP range will still make the exercise difficult; but at least the possibility will be there.

sounds about right ! it will prevent unwanted ACS Defend & still serve the purpose of extending interception possibilities