Thirsty, I have something like that for my HLT, but for my BK I will need more, as I do 10+ gallon batches. But that is interesting. Where did you find that? The thing for my HLT is a bucket heater available at farm and ranch supply type places.
I like the idea of a controller to handle different size batches and controlling the boil by just turning a dial. I'm not so big on unplugging 240V things while they are running. But I will consider your suggestions, in particular in the short term. As we've found out, these controllers aren't cheap. Given a controller, it could also be automated, but I'm not sure how well a PID can control the boil.
I hadn't thought about insulating the BK. My current HLT is insulated, and I was going to Armaflex (or equivalent) my next one. But I chill in my BK as well with an immersion chiller. I'll have to think about that. I could make the insulation easily removable.