Can't create site to site vpn in ARM for a policy based vpn

I'm following this guide https://azure.microsoft.com/en-gb/documentation/articles/vpn-gateway-create-site-to-site-rm-powershell/

and need to use a static public IP since our Palo Alto firewall requires a hard coded gateway IP (only supports policy based vpn / IKE v1 - NB we can't upgrade to PAN_OS 7 which does support IKE v2). 

The Azure virtual network gateway will not accept a static public IP address.

This was not a problem with Azure classic networks and we have been running a tunnel for a number of years.  My understanding was that the gateway IP was static in classic

So how does ARM support policy based vpns?

Thanks

David