If you want to automatically add Unity components to your HDA's output gameobjects, then you can easily do that by creating a detail string attribute to your geometry with the name “unity_script”, with the value being the name of the component. Multiple components can be specified as well, and these components can be anything from built-in Unity components like Colliders, Animators, etc., to your own custom Components.
Attached is a simple HDA that takes in an input geo, and assigns a BoxCollider component to the output.
More info here: https://www.sidefx.com/docs/unity/_unity_scripts.html [www.sidefx.com]