We do not have any suggestions regarding that case. In general, that should not be related to the Page Builder that you use and more of the page or post structure of WordPress which Cornerstone does follow the same rules.
The nest case scenario should be a user role that can not publish and only can add drafts. I think the Contributor user role does exactly that:
So you can simply go to X/Pro > Settings > Permission and then from the Permissions section you can select the elements the contributor can use:
For more information about the Permissions please check here.