I'm just about to unpack my M200 and don't have any practical experience with it yet.
Since I read a lot about warping issues I had the idea to build side covers with integrated PCB or silicone heatbeds to reduce the temperature difference and control the cool down process. With that method you only heat up the build space and not the whole printer like it's done with heated chambers (where you end up with jammed filament according to other users)
As far as my experience goes you need something around 0.2 W/cm³ for the heatbed to heat up to about 60 degrees which would be a good start I guess.
Temperature control could be realized using an arduino board.
Don’t take this the wrong way, but I really don’t think it’d be worth the time/resources. Since you’ll have covers on the sides, you would essentially be making a much more complicated and less efficient heated chamber. I think you’re trying to keep the carriage cool, but it’s primarily inside of the chamber, and heat rises so it’d still get just as hot, and now you’re using a lot of extra power since the heat is going straight out the top.
If you wanted to do something ambitious, I’d suggest a closed build volume with water cooling to the carriage; you’d get an efficiently heated volume and protected electronics. The caution with this though is you want to be VERY careful about adding weight to the carriage or hindering its motion in any way.
The primary issue is not actually with the electronics underneath (though this is still a concern), but with overheating the electronics and pre softening filament in the carriage (aka printhead). I think the stepper is only rated to 50c and I think the main control chip in there is too (don’t quote me on those numbers), so these would wear out quickly if you were to get anywhere close to that. You could remedy this by providing cooling, but adding weight to the printhead or adding resistance could negatively affect print quality and even increase wear on the axis steppers. So if you do it you’d want to add minimal mass and not add any resistance (e.g. pulling tubes around).