I am not sure how the smart meter has changed the playing field, before the smart meter the meter reader needed access to the meter, so it had to be the standard key.
Today the supply can be cut remotely, and the meter is also read remotely, so there is really no problem fitting any lock you like. The problem is the faraday cage, if the cabinet is made of metal it would need an aerial outside the box, and if made of plastic, then clearly it is easy to smash.
However you will be better starting a new thread, as being 7 years old, answers given today may be wrong to the original question.