When in movie mode one can apply 4 effects that are applied on recording only - but cannot take for example negative photo. Is this some sort of hw limitation, or was intentionally differentiated? Shoting negatives is a low cost of 'scanning' analog films. While converting dozens of positive photos (of negatives) to negative (to make them positive) is rather a simply task, negative preview in M mode is something worth having. With custom WB it would allow direct negative 'scanning' with minimum postprocessing.
Start researching here: www.magiclantern.fm/forum/index.php?topic=1915
Digital ISO can be applied to photos (http://www.magiclantern.fm/forum/index.php?topic=1915.msg30972#msg30972); no idea about others. Maybe try them?
(edit: tried the negative effect on 5D2, camera locked up)