To Microsoft: you have an army of super developers, if Microsoft would just focus a small set of resources to enhance the user experience by adding functionalities like this one by providing out-of-the-box controls/components, PowerApps would rule.
I hope you could consider to have the drag-and-drop functionality for Documents with SharePoint integration.
It would enable model-driven apps to drag-and-drop files easily, and also while using the Dynamics 365 App for Outlook. This would make super easy for users to drag-and-drop files from the windows file explorer -or- an email to the model-driven app interface and store the files in the connected SharePoint in the back... See screenshots below for reference.
From Windows File Explorer to a model-driven app; (related) Documents control with integration to SharePoint...
From the Outlook inbox - email attachment to the model-driven app through Dynamics 365 App for Outlook.