ModelProcessor.cs

class ModelProcessor : AssetPostprocessor
{
    public void OnPostprocessMeshHierarchy(GameObject root) {
        var importer = (ModelImporter) assetImporter;
        var exposePaths = FindTransformPaths(root.transform, (path, name) =>
        {
            var includes = new[] {"Neck", "Head"};
            return includes.Any(name.Contains);
        });

        importer.optimizeGameObjects = true;
        importer.extraExposedTransformPaths = exposePaths.ToArray();
    }

    private List<string> FindTransformPaths(Transform transform, System.Func<string, string, bool> isExpose, List<string> paths = null, string parent = null)
    {
        paths = paths ?? new List<string>();
        var path = parent == null ? transform.name : parent + "/" + transform.name;
        
        if (isExpose(path, transform.name))
        {
            paths.Add(path);
        }

        foreach (Transform child in transform) {
            FindTransformPaths(child, isExpose, paths, path);
        }

        return paths;
    }
}