Think about it. Microsoft would not let any third-party or external company install unknown (potentially dangerous) software in the name of Windows Update. If that were the case no one would buy Windows.
Only the following are acceptable to be installed with Windows Update:
Any other case would lead to catastrophic consequences for Microsoft.
I don't know what you are trying to achieve (or for what "beneficial" purpose), but it's not possible.
Below are some sources from Microsoft
Concerning Windows Update running third-party updaters, (now former) President of the Windows Division Steven Sinofsky had this to say:
Microsoft Update (...) offers updates for Microsoft products and for 3rd-party device drivers. All of these updates are carefully screened, and must adhere to the Windows conventions.
And goes on to justly note that:
(...) you never know when or how updaters will run and what they might do
which is completely justified given the above reasons in this answer.