Okay. First a little discussion...
After a little research and trial/error, I've found that the Microsoft DirectX Web Updater for 9.0C will not work on Windows 10. It gives a proper message that it's for earlier OS's, and then closes. The only way to get it in Windows 10 is with the full "end-user" download. The issue here is that the files and executable are about 100MB in size, and it will need to be added to your game size. The alternatives are making your games "not for Windows 10", or forcing the user to download the full developers update, unzip it, and run the executable manually.
My thoughts...
Making your games "not for Windows 10" is unacceptable.
Assuming that the user would want to or even know how to download, unpack and install the update is once again... unacceptable.
So...
I'm thinking that when the launcher initializes, it will...
1. Check for DirectX 9.0C and offer a choice to "Update DirectX" if not found.
2. If user chooses No, a message will inform them that the game cannot be played and will exit.
3. If user chooses Yes, DirectX will be updated from the DirectX folder in your package (if it exists, otherwise a "contact the vendor" error message)
What you would need to do...
Copy the DirectX folder from your FPS Creator Directory to the Launcher directory.
Let me know your thoughts and ideas.