Please add an Export option to NOT delete any files within the export directory (apparently similar to the Publish via FTP behavior).
For safety, this should probably even be the default setting, with the need to opt in to the current destructive practice of losing all other files and folders in the export directory.
The use case is that I have PHP scripts run using Code Widgets that have additional asset dependencies (other PHP scripts as well as image files which are modified by PHP before presentation), and these asset files are deleted without warning on Export, which is really kind of terrible behavior.