@aemninjaI believe it is possible, please have a look on dialog implementation of Workflow Initiator Participant Chooser step /libs/cq/workflow/components/workflow/initiatorparticipantchooser, it is using following ecma script /libs/workflow/scripts/initiator-participant-chooser.ecma.
I think base on above you should be able to modify your workflow step to have all you need.
