I suggest to add Padding and Custom aspect ratio on Video effects control panel where changes immediately affects playing video. Together with Cropping these 3 effects completely covers all usual needs of users.
CROP - removes redundand black pads or unwanted borders (already available!).
PADDING - adds black (or custom color) pads for example for subtitles.
AR - chandes display aspect ratio completely according to needs of users by changing actual displayed width (+/-) of a video. Together with displayed height it gives custom display aspect ratio (w/h). There could also be a list of sorted standard aspect ratios 4:3 (1,333), 16:9 (1,777), ... indicating which one is a custom change approaching to.
>> How to crop and stretch?
A filters and effects window (control panel) should stay in front of (over) VLC player window (VLC 1.2.0 is trying to hide it) and should be also available in fullscreen mode.
Thanks