Software defined man in the middle attack.

Hi,

I was looking into sniffing and traffic analysis and found that hubs are a scarce today and using a switch to "arp poison" the network is borderline cracking.
I would like to know if its been done before and if not if its theoretically possible.
I want to connect a target to my laptop, and via a USB to Ethernet adapter the laptop to the network.
The laptop will be inline with the target and the network, some sort of physical man in the middle attack.
Finding a HUB that is USB powered (everything has to be mobile) and does perfect port morroring is difficult.

There is a product out there called the "Star LAN Tap" but its a directional sniffer and not practical.

Thank you guys and have a great day.
Enkm.