The default Remake edit popover (that pops up when clicking an element with an edit: attribute) has default styles applied to it and can't be customized a lot.
It would be nice if a user could make a custom edit component and insert it into the edit popover.
This will probably require some thinking around how Remake can support a plugin architecture in general.
There are already some plans in the works for supporting checkboxes and radio buttons the edit popover. But advanced image uploading and cropping control would be a great additional plugin that probably wouldn't be in the core Remake library.