Thoughts on Eneri (Corridor) Sector etc.

[BRJN]

It occurs to me that dropping off several Voyagers / New Horizons, carefully placed and optimized for the purpose, would get you a bigger "sensor dish".
Or - hello post-Virus recovery era - a spool carrying 10 km of cord to reel out with a sensor attached on the other end (make that cord a bungee cord and the sensor will come back by itself).

 

[BRJN]

Still, any other thoughts on the OP (First Imperium border creep) or on the star Deneb?

The Vilani have plenty of time before the Vargr discover them. After that happens, I would expect 'anchoring the border on the Windhorn' becomes a big deal for The Authorities. Because letting raiders through that narrow gap to the interior is just silly making extra work for everybody.
Once other Vargr arrive having gone the long way 'round the Windhorn, this becomes a 'just the way things is' headache.

 

[BRover]

It occurs to me that dropping off several Voyagers / New Horizons, carefully placed and optimized for the purpose, would get you a bigger "sensor dish".
Or - hello post-Virus recovery era - a spool carrying 10 km of cord to reel out with a sensor attached on the other end (make that cord a bungee cord and the sensor will come back by itself).

I was referring to that sort of idea:

2. The possibility of different perspectives is helpful as well, especially if there is some way to get longer VLBI sensing. Maybe scouts/military ships have some kind of deployable sensors for the purpose? It would seem very doable to get a few hundred meter diameter dish, rather than a meter or so (single sensor) or a few meters (ship hull sensors). Likewise, ship's smallcraft could serve the purpose.

But, yes, either tethered or free-floating sensor platforms.