Possible fixes to "Non-tunable struct parameter 'CNTLR' is not supported for Code Generation"

When performing code-generation using Embedded Coder for SIL testing in Simulink Test, we receive this error:

Our entire control system is currently parameterized using structs such as: CNTLR.LowVoltageSystem.MaxVoltage = 12;

I was wondering what solutions may exist to fix this problem, beyond replacing all of the constants within our controller with non-struct variables.

Any help is appreciated.