You dont have to detect them. Why even?
Look at them. NVGs, gun, gear .. you see what they have. Do you want to magicaly look into their backpack from 50 meters away? Why do you want to camp a body? Kill him or them fast in the right moment (you waited for), go to loot and dont take too long - just the most valuable stuff you need or want and get out ASAP. Run into a direction they dont think you went and maybe hide for a minute if you know they are back. Cat and mouse. Or kill them again and go on.
Enemy COP nearby where they can respawn? Attack it so they cant spawn there.
I killed people on the supporter weekend .. it was rewarding enough since it was tons of loot. I have more sights, NVGs and guns I could really use all the 0.4 update long and its just a week now lol.
Making PvP more "valuable" makes it into a arena shooter in the end where the PvE is not the main target anymore. As you said yourself, its a PvEvP shooter not PvPvE.
And even if the loot is not rewarding, the fights are mostly. Yesterday I and two friends took on three guys in Blue Lagoon. We sneaked there and thought its a single player. So we didnt take on COP Aresenal. In the end we killed all three of them but hell broke lose when they of course came back and back from arsenal. It was a cat and mouse game in the forest east of Blue Lagoon. After some time a second squad of two players came in Kilo 3. We chatted a bit and made a plan. They took on arsenal. We pushed the enemy players.
In the end we didnt need any of the loot. The experience was all we needed. It was like a freaking Vietnam situation lol. One small mission (we didnt want to finish a task or anything, we were hunting and roaming the world) lead to a full blown war just as in 0.1, 0.2, 0.3. No need for insured gear shit to retrieve back lol