If I had to choose between auto expansion of "if space" or the completion thing I describe, I don't know which I'd choose. (They're all much more important than organizing file tabs with drag and drop though - an option for showing open files in the left pane (instead of files of highlighted package) would be more important than reorganize file tabs too! - in my opinion ...
But there are no open files in TheIDE There is just one file you are editing... Means only possible thing is some form of LRU list. And never forget to use Ctrl+Tab, that is the best option for dealing with LRU files AFAIK.
Anyway, I will consider adding <LRU> pseudopackage....