Providing assigned users properties in cascading control would have a huge benefit where relation is established on a project between a category e.g. Work package and the users that need to interact with this Work package.
Case scenario:
WP1 - PM John Doe
WP2 - PM Prentice Willson
When WP1 is picked in parent cascade, then Child cascade will have option for only John Doe. When selected the AssignedTo property has John Doe as value. If the child binding is made automatically where only one value exists even better.
Thank you for submitting your idea. We understand the desire for it and will consider it for a future release. At the moment, this could be partially achieved through actions on the form itself and we plan to add more functionality through conditional workflows that would further address this need.