Here was my thought for dealing with the free Intel provided by Local…
Leave High and Low Sec the way it is. These are faction space, and the factions want you to register yourself with the local channels the whole time you’re there.
Unclaimed Null Sec loses Local functions completely. Nobody owns it, nobody’s paying the bills, so the local channels are offline. Your name only appears if you speak in chat, and it disappears after 5-15 min of silence.
Claimed Null Sec has the option of reactivating the local channels. Maybe it’s a deployable, maybe it’s just an I-Hub upgrade. But it allows them to turn the registration stuff back on… So long as you enter the system through a registration checkpoint. That means if you jump in through a Stargate, or you undock from a station, your name will appear in Local (possibly only for the 5-15 min timer as before). But if you enter through a wormhole exit, or by riding a Jump Bridge, you will not appear in Local unless you speak. And maybe you can set it up so only non-Alliance members appear, that way you don’t advertise how many of your allies are in system.
This means a single Cyno alt may appear for a time when they sneak into the system, but the fleet they invite in later will not. And the invading fleet will have no idea exactly how many of you there are ready to defend.