thwarting the "bump key"

Together with different length drivers so the pin stacks are appooximately the same height. Possibly also small magnets at the tops of the lower pins and the bottoms of the drivers so they stay together when bumped.

The choice of materials for key and lower pins, key cut and pin bottom geometry, and spring design should all be such as to enable the stiffest possible springs to be used consistent with ease of inserting and removing key, and wear on keys and lower pins.

This is not a bad idea but you are going to find operating problems in a lot of low end locks with a significant increase in spring pressure.

This actually is a good idea but discreet magnets are obviously not practical. Why not use steel pins with either the top or bottom pins magnetized? If hardened steel drivers were used this would make drilling much harder as well. Again though poor tolerances in some locks are going to result in operating hangups. Due to the increased reistance of the pins to separating at the sheerline.