The duration of starting to create a free text invoice based on Configurable Business Documents in non development sandbox environments is more than twice as long (50 seconds to 20 seconds). For a regular user having to run more than 300 invoices a day this is not acceptable.
Create an option, to run this invoices as an reliable asynchronous service, so the task can be send to the server and the user can continue working and will get a notice, when the invoice document is finished.