I am primarily using Kdenlive to cut my underwater videos. One feature I am desperately missing is a decent way to correct the coloring of the video.
Water absorbs different wavelengths at different depths (the higher the wavelength (blue), the deeper it penetrates. That's why most diving shots have a distinct blue hue. If there are a lot of algae in the water (especially in fresh water lakes) then you get a green hint.
In the first couple of meters you can reduce the effect by using a red filter, but usually you need to adjust the colors in post production.
So what I envision would be a key frameable white balance filter based on the filter that gimp uses for stills. (the auto white balance is highly effective for photos). So one would select the frame, hit auto, adjust perhaps the aggressiveness of the filter, go to the next key frame and repeat. The settings of the filter like (e.g. magenta<->green) would be morphed between the keyframes, just like other filters (e.g composite)
I am no programmer, but a willing beta tester :)