Not speaking for VMware but offering my opinion: the option you are asking for will come when VMware implements bridged networking[/i] to your MacPro's network interfaces. Bridged networking is a feature of all other VMware products such as Player, Workstation, Server and ESX Server. It is also a feature of other Mac virtualization products.
Currently Fusion supports network address translation (NAT) networking which uses any available network connection on your Mac, in a sense "all connections". This is the most practical form of networking for connection-rich systems like a MacBook and MacBook Pro. While a MacPro can have wireless connections, bluetooth and USB connectivity, I would venture more than 90% of MacPros are wired. You'll be able to restrict your Fusion VMs to a the second network connection soon enough.
