also unlike dashcams, massive enclosure, good heatsink properties, reflective surface and not sitting behind a window in a locked car that's 30°c to 40°c above ambient temps
With the exception of good heat sink properties everything else you mention isn't really accurate. Many of today's CCTV cameras are quite small actually and many are black or charcoal gray. Most importantly you ignore my mention of the most significant difference between dash cams and CCTV cameras and that is that unlike dash cams which have housings that are as well ventilated as possible, CCTV cameras are hermetically sealed and the electronics and lenses inside these hermetically sealed containers can spend hours and hours a day baking in direct sunshine, and they run 24/7 for days, months and years on end. The notion that a hot car interior would be any hotter or more stressful to the components than the inside of a hermetically sealed CCTV camera baking in the hot sun seems like a fantasy.
None of my CCTV cameras have ever gone out of focus or experienced a component failure with the exception of some IR emitters that do eventually start to fail as they approach end of life after about 50,000 hours or so. Cable and connector failure can be a problem after long periods out in the elements.
Recently, I've been dismantling and examining several old CCTV cameras that have been taken out of service. The primary reason these cameras were taken out of service was indeed some, but not all IR emitters failed plus the fact that the sensor and DSP technology had become obsolete. My tear-down research has led me to certain important conclusions about these cameras. I agree with you completely about heat sinking. It seems many CCTV cameras go to the trouble of mounting the the PCB and other components on a metal plate and heat sinking is always a priority. More significantly each camera has revealed that all the components, including the lens assembly are mounted in a very rigid "cage" structure that prevents any kind of warping of any of the assemblies due to temperature changes. In some cases plastic parts are used along with metal ones but in all cases rigidity appears to be of paramount importance. The lenses in these cameras are also always very well supported in such a way that they cannot move around or warp due to temperature extremes. In some cases the lenses are not only in metal modules and have metal barrels but they are inside a metal sleeve that keeps the lens bezel rigidly in place. The main thing is that virtually every CCTV camera on the market is made with a cast aluminum alloy housing, not plastic. There are a few coming on the market now made from high tech polymers or FRP.
Comparing the design and build quality of the average aluminum alloy CCTV camera and the average dash cam the differences seem dramatic. Dash cams, with their thin plastic housings with a circuit board screwed onto molded in stand-offs bear more of a relationship with your average electronic gadget or toy than to an actual "camera". The same comparison holds true to film and digital cameras I have dismantled which regardless of price are built
much more rigidly and to a higher standard than any dash camera I have ever taken apart. Interestingly, you can buy a very high quality CCTV camera today for about the same or even less than a decent dash cam.
Ultimately what I believe is needed in dash cams is a new paradigm where dash cams will be designed and built more like miniature CCTV cameras. Imagine a small, cast aluminum alloy housing that is extremely well ventilated, possibly including heat sink fins and an extremely rigid internal heat sinked mounting platform for the PCB along with a rigid metal lens support. This would make for a camera and internal components that are unwarpable and that is engineered to shed heat as efficiently as possible.
A camera like this could also borrow a really cool feature that I'm sure would be very appealing to dash cam buyers much the same as it is to CCTV cam buyers, perhaps more so and that would be vari-focal lenses that will never lose focus regardless of temperature extremes. Oh, and maybe an integral sun shade like we often see on CCTV cameras would also be a nice feature. Hopefully, one of these days some intrepid dash cam developer will take this ball and run with it.
Here is an example of an extremely compact, very well made, black, hermetically sealed CCTV bullet camera that can endure temperature extremes for extended periods of time. With a different mounting scheme a camera like this wouldn't be too much different in size than a dash cam.