Just for interest...
I am just starting to look at the code for missiles detecting their own targets. I was aware that the new sensor changes would make missile sensors much more effective (which is why I added the rule about 0.25 MSP minimum). However, seeing it in action will be quite different than the theory.
For example, assume we have a race with active sensor tech of 21 and EM tech of 11. A VB6 active sensor with resolution 100 and size of MSP 0.25 (or 0.0125 HS), with active strength of 0.26, could detect ships of 5000 tons at 285,000 kilometres. The same missile sensor in C# Aurora will detect 5000 ton ships at 4,430,000 kilometres.
If we change the above active sensor for a Thermal sensor of the same size (and assume Thermal Tech 11), it will have a thermal sensitivity of 0.14. The Commonwealth Tribal M class destroyer (standard laser-armed design of 6365 tons) has a thermal signature of 650. The VB6 version of the sensor would detect the ship at 90,000 kilometres. In C#, the range will be 2,370,000 kilometres. That range gap will drop though for more powerful active sensors and for larger target ships. The C# passive advantage is more pronounced for small sensor and small signatures.
Finally, lets change the above active sensor for an EM sensor of the same size, which will have an EM strength of 0.14. Now lets assume we want to use that missile for a HARM attack on a ship with an active sensor using the same tech. Lets say size 3, resolution 100. In VB6, the missile sensor will detect the ship-based sensor emission at 882,000 kilometres. In C#, the range will be 7,424,621 kilometres. That range advantage will drop though for more powerful active sensors or more powerful emissions
Even so, there is a lot more scope for passive attacks and mines will probably become effective in other places beside jump points.