What is the worst that could happen connecting the neutral from a smart switch to ground?
There are two main problems:


Since building codes doesn't allow such usage, any inspector who sees it is going to flag it and likely want to inspect a lot of other wiring.
If used in a circuit which is GFCI/RCD protected, any significant current the device would feed through its ground-connected neutral would likely cause the protection device to trip.


I don't think there's any technical reason why it shouldn't be possible for a manufacturer to create a class of switches which would be approved for use in such fashion [ensuring that such switches would never pass more than a fraction of a milliamp through the neutral lead even at startup would require extra circuitry, but that would not be an insurmountable problem.]  I would expect, however, that manufacturers have no motive to build devices which regulators would not recognize, and regulators have no motive to recognize devices that don't exist.