2016 was a tricky year as there were three fairly distinct variants of cars produced with a lot of changes. You reference 2016.5, so I expect you are referring to one build after roughly end of April that has the revised front fascia without the original black oval. Now of that configuration it is important to distinquish if it is an AP1 version, produced before mid-Oct 2016, or the beginning of the vision based AP2 system produced after mid-October 2016.
If the ability to have features such as dash cam, sentry, and some of the more FSD type of capabilities, then you need to be looking at a car after that mid-October 2016 switch.
I owned a June 2016 MS90D for 7.5 years (purchased new, sold early Jan 2024). I put right at 80k miles on it in that time. My config sounds similar to what you are looking at; coil suspension, pano roof (sunroof).
I did have a rear drive motor replaced under warranty due to what seems to be a very boarderline limit spec electrical characteristic. This was replaced under warranty after it tripped fault code for the second time over the first 2 years of use. Since then, there were no issues with major battery/drive motor related systems.
There are a few typical failure modes which many commonly reference with this vintage car.
- door handles ... multiple failure modes. I ended having to have two repaired (driver side front and rear, which were ones most used).
- Headlights where the "eyebrow" daytime running light tends to yellow from the center outward. I had three replaced under warranty. My passenger side was showing signs of yellowing when I sold it. Had been that way for last couple years and chose not to replace it. It's in my view cosmetic failure, as the main headlight function is not influenced. Some view it is more a functional failure. These are expensive. I've lost track of replacement cost, but it's upwards of $2000 each as the whole assembly must be replaced.
- Leak in cooling system due to issue with one of the multiple 3-way/4-way coolant valves. I experienced this in mid 2022 as I started to see a very indication of fluid on my garage floor under the front of the vehicle. Ultimately I had a low coolant warning, so took it in for service. In my case the one valve needing replacement was about a $400 total repair via my local Tesla service center.
- Pano roof assembly. You can find reports of various issues. One of the most typical is leak of some form. There are two drains at the front which can get clogged, which can cause water to leak in and stain the headliner. Others can be issues with the seals around the opening. I never had any issues with mine, but over the first 4 years I took my car in for annual maintenance checks which included cleaning and lubricating the tracks. If you do get a car with a pano roof, that might be something worthwhile doing on a periodic basis as preventative maintenance in my opinion.
- MCU1 main display eMMC failure related issues. There is a safety recall that will cover the replacement of the eMMC memory chip, but many still seem to report various problems with aging MCU1 type of display units. The ' big hammer' approach to fix this is to upgrade to MCU2. I elected to do that on mine in Dec 2021 and will tell you for me it was well worth the ~$2000 I spent. It includes full replacement of both the main display and the dash instrument panel, which addresses any potential leak/bubble issues around the edges you might see, plus you'll enjoy much faster navigation system and main screen performance, as well as the ability to stream video via the "Theatre" app.
Now not a failure per say, but cars of this vintage are starting to see an alert pop up about the need to replace the main battery fuse assembly. This seems to largely be a time base thing with people start seeing it around 7.5 years. That was exactly my case. Tesla did replace this for me under my 8 yr/unlimited mile main battery pack warranty. Out of warranty they were showing was about a $250 repair.
Those are key thoughts on mine on the vintage of car you are considering. While I know free supercharging seems like a big deal, I suggest you to first really think through whether having the 8-camera AP2 level versus AP1, and pack size/range considerations. Ultimately I feel those are much bigger factors on whether the car fits your needs.
I understand the lure of FUSC. Tesla's offer to allow me to transfer that to a new Model S in Q4 last year was the tipping point that caused me to replace my 2016 MS90D with a new 2023 MS LR. I'll be the first to say that was as much an emotional vs. financial/rational choice, but hey, I'll readily admit I'm not always 100% totally logical/rational in my purchase decisions. Honestly, I think that FUSC was worth maybe about $5000 over my 7.5 years of ownership with about 45% of my total driving and energy use being via free supercharging. But instead of focusing on just that factor, I'd first focus on what is your real range needs, would a 90 or 100 pack be a better choice, plus whether some of the capabilities of AP2 or new vs. AP1 are important to you.
Good luck with your purchase decision