Somewhere in one of my past posts some time ago, I recommended a Default Folder for upload setting (like in Preferences) and your override suggestion (for session) on the main Image Uploader page would be helpful too. None has been added.
However, I eventually adopted use of the Drag and Drop, where I can set the folder at bottom for all the images in one pass. The Java uploader has similar feature at the top, so getting it working is your best alternative. If Java isn't working, it may be due to a browser setting or Java not correctly installed.