first iam new here and don't know the rules, iam only want to share my idea.
iam from germany so please excuse me for bad english.
The first thing I really see as a necessary feature is that you can fast-forward / rewind when opening video files in the browser, the second would be an arrow button with which you can play the next video file in the folder of the opened file you don't have to keep reopening the files if you want to see everything in a folder. This also applies to image files.
Another useful feature that Opera would do better than other browsers would be an integrated PDF editor, with which you can fill in text fields in PDF files and then save them.