My use case is this:
Editors upload images to nodes. These nodes display the images using two view modes, one square, the other a scale only. The square is for teaser display, the other for the node view.
I've been using SimpleCrop, a new and elegant JS crop module. Unfortunately, it does not support two separate crops (ie image used in separate view modes with separate image styles).
I feel that Focal Point is an excellent idea, and I think that if it was to support the SimpleCrop widget type for image fields, it would be quite cool. I imagine the config page would contain a new option to enable support for SimpleCrop fields, and then you would configure the image styles as normal with both the SimpleCrop action and the Focal Point scale & crop. The tricky part would probably be to render both widgets on the node form an retain good UX.
TL;DR: I think Focal Point would work well with a manual cropping solution that supports cropping multiple image styles.