Some have done this modification. An option for adding a plug is not shown in the Tesla Gen3 Wall Connector Installation Manual. Because Tesla does not include instructions for adding a plug to the Gen3 Wall Connector it would not be code compliant.
If you have an existing receptacle then use the Tesla Mobile Connector or the Tesla Corded Mobile Connector (this version of the Mobile Connector comes with a fixed 14-50 plug). The Tesla Mobile Connector enables charging at up to 32 amps, the Tesla Corded Mobile Connector enables charging at up to 40 amps with the fixed 14-50 plug.