BP doesn’t have a way for you to give users the ability to approve a BP deployment before it begins. They would have to initiate the installation process themselves, as described below.
I would recommend you put all of the necessary files on a shared folder on your network, and then provide a link to each user such that when the user clicks on the link it executes a script (really can be just a single command) to install Windows 10 1903 silently.
-Doug