Simplygon is the perfect tool to optimize your geometry with. But sometimes you want to keep things as they are. Vertex locks allows you to protect geometry from optimization. This is how to use them in Maya.
The LockSetVertices flag is a bit ancient so it might work with varying degree with cascaded pipelines and other features.
Command line used:
Simplygon -LockSetVertices "locked_set" -sf "C:/Users/USER_NAME/Documents/Simplygon/10/Pipelines/50_reduction.json"
Simplygon command:
documentation.simplygon.com/S...
Vertex locks:
documentation.simplygon.com/S...