Such property will allow the developer to choose whether the warnings will be displayed as RadAlerts or standard browser alerts. In this way the built in WindowManager could be user for showing RadAlerts.
Please consider adding file editing into the RadFileExplorer (could leverage CodeMirror). Would be a great help to sitefinity to be able to edit the css or less directly on the fly in the fileexplorer.
Add configurable option to create a thumbnail for uploaded image and use it in the thumbnail preview mode if one is available