here are the best pics I have of my dads shopbot. It is only 3 axis but it may help you get a better idea of what it will take. I think you could dedicate one side of the machine to the wood turnings and the other end to plasma. If the parts are small most of the time it would work well. The only thing you would need to do to switch between the two is to swap the router for the plasma torch. Check out the plasma build logs for an idea of how guys are mounting their plasma torches. One thing to cosider with the shopbot, I am not sure if the control is capable of THC (torch height control). It maintains the torch offset from the workpiece as it warps, etc. It is not vital but is really nice to have.