Summary: New radar building and research which doesn't scan in all directions and in the immediate vicinity, but instead a player-defined patch at any range provided enough power can be supplied.
Details/thoughts: You plop down a vanilla radar, it consumes 300kW and immediately gives you I think a 7 chunk diameter of visibility. In this proposed mod the player needs to research a late-game building (with military packs) which is also expensive to craft (think spidertron expensive) and keep powered. When placed the building would make a small power drain but give no benefits. There would be a separate remote (or maybe a radar planner item much like a blueprint/decon/upgrade planner) unlocked with research which would be used by the player to target a range of chunks for targeted reveal. The further away these chunks are away from the building, the more power hungry the building is. The building doesn't auto-reveal either, it needs some time to scan the area. It might consume hundreds of megawatts to scan the chunks at a distance (maybe hundreds of chunks away) but then only consumes tens of megawatts to keep the chunks scanned & visible in the map view. The remote or planner could be used to cancel the chunk scanning/visibility to cancel power consumption. Tearing up the modded radar would kill any scanned/scanning chunks.
Why: The building might be used by players with very aggressive biter mods/settings. If a defense breach occurs the player can remotely view the area to see the damage and react at the cost of power draw. Alternatively if the player makes a mistake doing a remote deconstruction and takes out power/vanilla radar coverage, they can use this building to fix that mistake without summoning themselves or a spider to the location.
Targeted/Directional Radars
Re: Targeted/Directional Radars
Two methods I know of to nearly do what you're describing; fire artillery where you're exploring, or the scanning radar mod; it allows you to describe minimum and maximum range, and start and end angle from the radar.