TL;DR
Using a new radar scanning remote item, map sectors can be targeted for prioritized scanning over the current automated scanning method.What ?
A new radar scanning remoteThis would be an inexpensive controller ( 1 circuit, 1 iron plate? ) with functionality comparable to the artillery remote. When held in the hand, the map could be targeted, leaving a radar targeting mark. Targets would appear, creating a queue of prioritized sectors. As radars in range completed their scan cycle, they would attempt to pick a prioritized sector to scan. If successful, the targeting mark on the map would expire, and the normal scan mechanics of briefly appearing visible on the map would occur. If there no prioritized sectors in range of the radar, it would continue to perform it's current behavior.
A separate extended manual range for radars
Again comparable to the artillery, the range for manually targeted sectors could far exceed the current automated routine.
Research extends the manual sector scanning range of radar, optionally also the automatic sector scan range.
one research topic, or possibly add this bonus to artillery range research to ensure scanning range exceeds shell range.
No buff to the always visible radar range