I think you could configure each port on the switch with a different default VLAN and plug those into the terminals (e.g. Port 1 gets VLAN 1, Port 2 gets VLAN 2, etc). That will by default separate each port into a separate network. Then use VLAN tagging on your XP VMs that you were going to spin up, so they each are effectively connected to a separate port on the switch (e.g. VM 1 is tagged for VLAN 1, VM 2 is tagged for VLAN 2, etc).
This is just the high-level details of what you'll need to do. Most lower-end consumer grade switches don't have VLAN support, so you may need to spring for a better switch, and make sure your VM software supports VLAN tagging.