Okay, but a power or port or communications facility can be a valid infrastructure target, and they sure as hell aren't full of combatants, so the 'combatant' designation is only part of the story. I think it's clear that some Gaza police are 100% combatants, and all are potential combatants, but that's only one way to make them legally acceptable targets. For example, Nizar Rayan was probably killed not because he was a legitimate target (thought he happened to be; his family was not) but because his home was a weapons depot and tunnel entrance. If the police as an entity are a legitimate strategic target, that clears up things quite a bit.

I also think you overestimate Israel's intelligence assets in the Gaza Strip. Their WB operations are far better.