I was involved in making a server that bricked itself if you opened the cover, for added FIPS security. So let me tell you all of the things that can go wrong:

Is the switch mounted on sheet-metal? Well you will discover that sheet metal bending is an imprecise process. You need to generate a mechanical tolerance stack-up that accounts for the worst-case opening. What happens if the server flexes a little?

How precise is the open point of the switch?

The sense side of the circuit is high impedance. The wire will act as an antenna and detect any noise in your device.

How can a user replace the battery without triggering the tamper detect?

How sensitive is your switch to shipping vibrations?

Anyway, the experience gave me a good appreciation for those who make landmine triggers :-)