Going by area covered instead is solid IMO. Real sensors monitoring a set area of space should require 4 times the strength to detect the same object twice as far away ( think of it as monitoring a 4 times larger area on the inside of an imagined sphere of double size around your sensor).
What I would like to see in sensors is narrow focused sensors. A sensor that covers only the forward 90 degrees should need significantly less strength to achieve same resolution, but at the cost of leaving the flanks vulnerable.
I also in general feel that passives are pretty underwhelming since they are useless for all warfare except "early" warning (which often tends to become late warning after your actives already are tracking them). Along this line Id love to see missiles with mostly passive guidance or passive launched ones actually work better to allow more sneakiness, even if missiles use on-board actives for final approach. If I can track where an enemy craft is good enough for ships to intercept it within beam range using only passives I see no logical reason why missiles couldn't do the same until they are within range of their actives.
Or perhaps you could have passives which can spot stuff further out, but also have a large "probably area" or "range of possible enemy emission strengths" in what they spot, so they work better in their intended early warning role.
I don't know what is needed, but currently I don't find passive sensors that fun or useful, although in reality passive sensors are super important, especially
Anti Radiation MissilesSomething that probably needs to be addressed anyways is AMM balance since missile agility scaling increase their interception chance to unreasonable levels after a few tech levels. If you are boosting missile detect range of HS1 sensors by almost x4 AMM ships can be made smaller, cheaper and more redundant so it might be even more important.
Two things I would like to see is:
1.) Missiles need progressively larger "guidance packages" the further away from ships missiles are supposed to operate ( they need to keep signal with the ship FC for guidance ), and/or some sort of minimum size frame as mentioned. This should also help against the commonplace AMMs as an offensive swarm weapon strategy to overwhelm PD/Enemy AMMs.
2.) Missile armor scales with techs ( such that AMMs need more then strength 1 warheads on later techs even against missiles with way less then 1MSP armor ).