I know this is an old post, but why is setting a pvid a problem? For vendors where you don't specify the pvid it will be the native vlan, which is usually vlan 1. If you don't want it to be vlan 1 you can create a "dummy" vlan, say vlan 4000, and use that as your pvid. The best practice is to have a matching pvid on both ends.
The Fortinet Security Fabric brings together the concepts of convergence and consolidation to provide comprehensive cybersecurity protection for all users, devices, and applications and across all network edges.