Very nice construction! But I was wondering if the fact that you are creating cold/hot spots doesn't hurt.
During active fermentation you have natural convection going which improves the temperature spreading, but when lagering this isn't the case.
I have a 120 litres conical that I currently chill with a stainless steel immersion chiller connected to a cooling unit. This is a bit of a bulky solution, so I like the peltier option...