Sera, you sound like you know what you're talking about. How well do you think a chiller type device would work in a keg? Say there was some long U shaped SS tube through the lid, with glycol pumping through it? Kind of like ice in a glass. But with the glass sitting in my dead freezer.
I know it's an odd idea.
Actually its a sensible idea using a chiller type devce to cool liquids like that, because the volume of the 'fridge' becomes as small as possible, meaning you have more room for insulation. More insulation, more stable temps and less power consumption. Also, dont use submersible bilge pumps - the heat from the motor is expelled into the liquid, as in, the pump is liquid cooled. Get an in-line pump, these generally have external cooling, or at the very least dont radiate their case heat into your glycol.
It would make sense to build a box, put your keg in a rubbish bag, fill between the box and the outside of the bag with expandafoam (heaps, like 15cm gap between the two) and make a super-insulated keg, which you cool via a glycol line. In fact this is kind of what I am planning to do for my fermenters, which will not require much cooling but still some.
I've currently been investigating these issues as I've run into issues trying to store my 4 kegs (with room to upgrade to 6.) Most fridge volumes/dimensions lie and don't account for the compressor box/crisper and fixed trays that make fitting kegs
efficiently into a fridge a danm nightmare.
Thus I am currently building a fridge from an old fridge, and a new box made out of cold room panels, which fit 2 rows of 3 kegs perfectly. Should be finished in under a month. Pics uploaded as stuff happens, to inspire...