Hashcat probably isn't the best model for clean code, since its primary goal is to squeeze every drop of performance it can get.
An alternative would be a precomputed hash table, similar to what `gperf` does. Requires more work in the build system though.
Are there examples of other programs that require this?
This is the reason why for GPGPU programs, you often supply the kernel/shader as C code or another intermediate representation (vendor-specific assembly), and the final compilation step is done by the GPU driver.
This all rules are optimized binary code that work directly on the data stream instead if having a runtime that applies the rules.