Microsoft has recently updated the guides and tools available to define a good governance of Sandbox solutions in SharePoint OnPremises environments. This update is completely updated with the recent deprecation of Sandbox code solutions in SharePoint Online and can be found here:
Basically, the new tools and guides prepare us for the future deprecation of Sandbox solutions in SharePoint OnPremises by releasing new feature called Managed Solutions Gallery. This new feature is available for SharePoint 2010, 2013 and 2016 and will allow SharePoint Farm Administrators (and delegated Admins) to centrally manage what Sandbox solutions are allowed on a SharePoint Farm. The goal is to minimize the use of these kind of solutions so we can be ready for the future deprecation of sandbox solutions in SharePoint OnPremises farms.