1. It is possible to keep the WF instantiation Form open, if the WF uses CGI or CGI like tasks. However, if the flow is broken by another task like Submit etc. then the instantiation form is closed.
2. The Livesite workflow uses a CGI task to call a custom java service that in turns calls a Open Deploy job. Using the standard Deployment task does not seem possible, if one wants to render the failure message back to the customer.