Ok I have an idea:
360 No Scope - You cannot send subs so that any projected interaction occurs where you can see it, at the time of sending the subs. No loopholes via navigator*. Only driller-less sub with queen can move between your own outposts.
*More rigorously, this means the navigator cannot be rerouted to an interaction that occurs inside your sonar range (i.e. where you can see it) at the time of rerouting.