Hi Rob,
My device is actually located within my obs so the rain sensor is not normally exposed to the elements unless the roof is open. The point of it was to alert me if the roof was open and it started to rain. At that stage I shut the roof and whatever got any rain drops on it would then need to dry out. I therefore don't really need a heater. It would be easy to add one and drive it from the Uno PWM pins if you needed it. I'm not trying to do remote imaging or a high level of automation - just seeking feedback of what's going on while I'm sitting inside the house.
In terms of cables, I've got USB and 12V power going to my enclosure. The power is only required for the anemometer and could run direct to that device.
Regarding the AAG, I think it uses a similar approach to the Boltwood in terms of ambient-sky temp to predict cloud. I think that gives quite a lot of false positives which is ok if you want to be sure however for me that would rule out a lot of nights I'd rather be capturing something. I'd also rather spend the $800 on something else. If all you need is the cloud monitor, this can be done with just the Uno and the MLX sensor - probably less than $50 in parts. I've added other sensors because I could and part of the exercise was learning to program the Arduino and build the GUI. If you really want wind speed sensing, with the benefit of hindsight, I'd probably consider one of these hot wire options as they are a lot cheaper and easier to incorporate in the project:
https://moderndevice.com/product/wind-sensor-rev-p/