Create a video cropping software that works on Mac and PC (Maybe Adobe AIR)

I would like an easy to use software product that will allow users to drag/drop MOV, MP4, WMV and other popular video formats into the software (or click and select from computer) and be able to crop the size to 16:9 and 1:1 ratios as default choices, and custom ratios to be selected by user if needed. User can then drag the selection to the appropriate area of the video and then crop it. Default setting for 1:1 ratio should be the center area of the video, cropping out the left and right sides. User can also drag corners of crop area to resize crop area. Output should be in as many formats as convenient, but at least mp4. Quality of output should not be lost (unless going down from MOV to MP4 of course, etc.) Another feature would be to be able to trim the video start and end points as well. Once this project is done successfully, additional features can be added to continue work on the software. Thanks for reading!