The integrated image editor could be easily replaced by the nicer and richest PicMonkey online tool. (http://www.picmonkey.com/)
PicMonkey is not limited to cropping and resizing. It's easy to add text (lot of integrated fonts), change colours, contrast, apply FX, borders, draw on the image, and so on.
With this tool, it's not necessary for you or your customer to upload/download pictures to fix or modify them. Everything can be done directly in the dashboard, simply click on the image in the file manager, and choose 'edit' in the menu.
Try it by yourself !
Here's a 'work in progress' preview of 5.7 plugin :
You need for now to install it by hand, no package available for now.
Download and unzip image.php in your website /applications/elements/files/edit/
It's a work in progress, please be indulgent.