I've visited the site now, and simulated a Covert Non-violent Shutdown, which I reckon is the hardest stealth mission you could do there - and that site is indeed one of the hardest places to do such a thing. A Covert Theft would be slightly less challenging. I intended to record it, but it seems I failed to start the recording. I had not seen this particular settlement before, but I had encountered the layout.
My simulated mission took 42 minutes from disembark to embark, including some scouting, false starts and reconsidering.
First step was simply approaching the building. I permitted a guard to scan me. Overall, whenever a guard wanted to scan me, I let them; later on this involved dropping cloned permission levels. I walked into the foyer and examined it; I saw the lab and security room were both restricted areas, with door access level 0 to security, 2 to lab, and 1 to medbay, IIRC. There was a data port and two control panels in the security room, but there was a full ceiling on it. There was also a civilian who wandered into the foyer from time to time.
First challenge was to satisfy the Covert requirement; since I planned to do a heist, not a theft, this required turning the alarms off. I sight-scanned the civilian and guard so I could track them both on the radar, and paying attention to their focus (they turn their head to keep track of others, including you), cloned the security level off the guard (2). Then I waited until the guard was above the security room, where he'd have the furthest to walk back to it and no line of sight to the door, while the civilian was also out of sight. At that point I crouched to reduce the sound of my footsteps, snuck into the security room, stood and activated the alarms panel, crouched again and returned outside the restricted area. Covert success; even though the guard would return to stare at the alarms panel, he doesn't switch the alarm system back on.
Next came identifying my target. The guard wanted to scan me as he came down the stairs, so I dropped my privileges. Then I wanted to find a suitable terminal, and suitable access level to see what was in each room. As it turned out, there were no sample containers or similar in the laboratory; thus this installation doesn't do covert heists, but thefts or shutdowns may be possible. To find this out I cloned level 2 access (don't remember whether from the guard or some other NPC), and I selected the terminal in the corridor just before the foyer; this because only the civilian patrols there. I didn't want to have a guard come scan me while I was using the terminal.
Having satisfied the Covert requirement, I decided I had to simulate a Non-Violent Shutdown. This meant I mustn't kill any NPCs, but must still access a secured (power centre is restricted area with level 3 door) system with an opening timer. This posed additional challenges; since I didn't want to alarm any NPCs during the shutdown period, I had to get into the power centre without cutting the door open, which meant getting through the entire building with a stolen ID.
As luck would have it, there's a buggy NPC placement, where two civilians wander the roof of the building. One of them was standing still and had level 3 access. Thus acquiring high access was easy (just make sure the other one doesn't spot me while cloning), though keeping it proved tougher. I avoided the restricted area laboratory, which is challenging to sneak within as there's at least one scientist moving about in there, a guard at each exit, and an additional scientist. Instead I elected to take the upper path, also complicated by the same guards; their patrol routes take them up and down those stairs. I sight scanned them at each end and snuck by hugging the outer wall when they were in the lower corner, the furthest from the bottom of the stairs and the upper floor door that I could identify.
So, finally having a level 3 access and reaching the power centre, now I could stand just outside the door and sight scan the civilian inside. Their route took them up and down the stairs, standing by the reactor controls from time to time. I waited for the moment they turned from there to head up the back stairs, snuck in behind them, activated the panel, and snuck out. Similar to the initial alarms panel. From there, I had to wait several minutes until the power plant shuts down.
This is when I have to plan for the SHTF moment. Once the power is off, all NPCs will be on alert, and they may swarm the power plant, as they know something happened there. But before then, there are plenty of NPCs watching all the exit doors. I was going to have to run for it under fire, and I had to pass at least three sets of doors, two civilians and one guard. I didn't want to cut a door open early as this would alert NPCs there before I made my escape. And with poor timing, of course the power plant NPC was at the controls when the plant opened. In a Heist mission, this would be a severe issue as they close containers again.
Anyhow, I decided to go for it; I stood at the power centre door as the power turned off, which kept it open while the entire base went dark. I immediately switched my shield on, rushed in to grab the power regulator, and rushed back out; the power plant NPC turned hostile, and as I was seen fined me for trespassing and took a few shots. Now with the base dark, I switched on my light as well, and made a snap decision to try for the less populated upper floor again. I'm not sure which of the scientist and guard in the stairs room, maybe both, saw me; but they also had a few moments to take some shots, attracting anyone in hearing range. I quickly rushed up the stairs, which took me out of view for the civilian at least (the guard has a torch), cut open the panel, and overloaded the door. These crimes, too, were spotted; so I now had 3 fines totalling 750 credits. Once that door was open, I rushed through, losing my attackers in the twists and turns.
Now I had a moment of respite. From here, it was a simple matter of choosing my moment to overload two more doors and get out. I still had tracking on all the relevant NPCs, who were now on alert since the power was out. I took a big jump once outside bypassing the guards, boarded my ship, and flew off.
Mission success... well, even if I just imagined my mission, it took forever, and I failed to record it. My method required use of the useful suit (the one with the cutter), simply because I'd be locked inside without it.
It's possible, but certainly not easy.