Import Remapping

AstcStuff.cs

public class AstcImporterMapper : AssetPostprocessor
{
	private void OnPreprocessTexture()
	{
		// TODO: this should be using the TextureImporterConfiguration
		if (assetPath.Contains("_XXXY") || assetPath.Contains("_SME") || assetPath.Contains("_A"))
			AssetDatabaseExperimental.SetImporterOverride<AstcTextureImporter>(assetPath);
		else if (AssetDatabaseExperimental.GetImporterOverride(assetPath) != null)
			AssetDatabaseExperimental.ClearImporterOverride(assetPath);
	}
}

[ScriptedImporter(1, new [] { "tga", "png", "jpg" }, AllowCaching = true, AutoSelect = false)]
public class AstcTextureImporter : ScriptedImporter
{
  // ...
}