I'll begin implementing shortly.
One thing I'll need very soon here (in addition to the JS color picker!) is the crop region & focus point editor.
Basically, start with /manage/pic, copy it to /manage/cropregion and make it so you can drag/resize a rectangle around some region of the scaled image, and also move a circle focus point.
Then, let people save it.
I'll do all the database stuff... just do the cross-platform DHTML to move the rectangle and dot. (and they should be in multiple high-contrast colors, so they're visible on all images)