This would be neat, especially in combination with these tiny CTs but it sounds to me that the space constraints would require some serious adaptations compared to the usual non-DIN variant. For one, using the TRS jacks is most likely going to be space prohibitive in that sort of application. Not to mention that if you’re looking at a DIN rail already, a stripped wire is going to be more convenient to work with anyhow. From there you probably wouldn’t use an ESP32 board as a daughterboard of sorts, but rather solder the bare chip to the motherboard. All things considered this would require some pretty different PCB layouts and make production of the PCBs quite a bit more complex (the ESP32s are all BGA packages AFAIK.) So all in all, it most likely would end up being a separate effort, I imagine.
(As a side note, I wouldn’t mind plain terminals and stripped wire for CT connections even for the non-DIN version. I think that would allow for a much more compact IoTaWatt in general and it permits a wider choice of CTs, given how much faster it is to cut and strip wire on whatever connector might be in place than it is to attach a TRS plug to a wire without one)