The Combine has some strange quirks with sensor sharing and I am not going to cover all of them here. I think the system could be much simpler. Before I make a suggestion though, I would be interested to hear if what I am seeing in a few places is the way sensors are supposed to be working or a bug.
The first scenario is with regards to viewing NPC bandit fit-outs. My experimentation shows the following:
-When within range of a player's vision, the fit-out is always visible
-When outside range of a player's vision, but inside the vision of a NPC equipped with a multiple sensor pack, the fit-out is visible if the NPC is not in the player's party but will not show up if the NPC is in the player's party.
This doesn't seem to make a whole lot of sense. If the bandit is within visual range of an allied and MSP-equipped NPC, the fit-out should be visible regardless of whether the NPC is in the player's party or not. Bug or feature?
The second scenario is with regards to entities with ECM and became apparent in the latest quest.
-Droids with ECM always can be seen by players, no matter what sensor power they are scanned with. (Vision is affected by stealth, not ECM, so this makes sense.)
-NPCs which are linked to the player by MSP do have their vision affected by ECM and will not see a ECM protected entity unless they have enough sensor power on the entity.
One would think that like PC vision, NPC vision is not affected by ECM. But it is, which seems rather inconsistent. Bug or feature?
Both these situations suggest to me that NPC vision is being treated more like vehicle/ship sensors than PC vision. Is the case and if so, is it intended?
Wait, why would an NPC be in your party but NOT in your sensor range?
As far as your other questions go I think they require a deep look at the code itself to ensure it's working as intended because it could be that something else is at work besides the scenario that you think is the cause of what you're seeing.
We'll call the NPC enemy a bandit and the NPC friendly a scout.
-When the bandit is in range of a PC's vision (with or without macros), the bandit's fit-out is always visible.
-When outside the range of the PC's vision, but inside the scout's vision, a bandit's fit-out is not visible if the scout is in the player's party.
In the picture below, you can see I have a scout in my party and with the scout's vision, I can see some bandits. Clicking on their avatars will not bring up the fit-out.
-When outside the range of the PC's vision, but inside the scout's vision, a bandit's fit-out is visible if the scout is not in the player's party.
In the picture below, you can see I have removed the scout from my party and I can still see the bandits. Clicking on their avatars will now bring up the fit-out.
In both examples, the scout was linked to me via MSP.