With next plugin version, we add scanner windows. So you can show the following panel to select a device:
and a second panel to show the full scanner interface:
The user can scan and you get a script triggered when a new picture arrives. The user can of course scan several pictures and you may want to display them in FileMaker before the starts a script to process the images.
PS: We have the same controls available for Xojo, so you can have similar windows there, too.