The arms race you mentioned already begun. First they stop putting opcodes in the manual but then people found out by bruteforcing opcodes and seeing the change in register.
Clear plastic covering is out of the question. 1. Silicon chips are sensitive to light. There's an issue with early raspberry pi model where the board would reboot if someone took a flash photograph. 2. You can't resolve nanometer detail behind plastic casing.
It's expensive, but worth it imo.