Flexible workflow

Dear Support,

customer would like to configure workflow for supplier invoices without PO. We are evaluating costs and benefits for the 2 options: parked invoices solution or workflow for blocked invoices. Thus we have some questions to be addressed:

1) Is the app Create Incoming Invoices (ex Fb60) able to be used in Workflow configuration? Create Supplier Invoice app would in any case create a temporary number for document even if no PO reference is entered, and this is not accepted by the customer. Is it possible to use Workflow for Blocked invoices starting from Create Incoming invoice app?

2) We have read it is possible to notify externally via mail (not via My Inbox app) the request of invoice approval to approvers. Are there any constraints in S4HC to set this kind of custom output type?

Thanks a lot

Kind Regards