The required feature described as a wish
As an implementer I would like to be clear on what the functionality of shared networks is completely and without ambiguity.
as shown in testing for #10612, shared networks are now allowed to support the functionality “Source NAT” , but as the VMs in a shared network have their own public IP, this does not make much sense. It would make sense if some plugin would provide “Firewall”, or “Packet Shaper”/“QoS" for the network however.
Investigation is needed (probably followed by design/implementation) to see what should be possible and how to deal with it in API and UI.