How to design a component which has N number of Avalon ST Sink ports in SOPC Builder

For up 512 sinks in a single component I would probably build that up as a composed .tcl component made up of smaller components internally (hierarchical component). Now a component with 512 interfaces I think will be pretty hard to manage in a graphical sense so using hierarchy I would make sure only the interfaces that need to talk to the outside world are exposed while the others are wired up internally.

If you stub out interfaces you can set the inputs to a known value so the only messages you should see are optimization messages. So when I say stub I don't mean leaving it disconnected which I agree would be problematic.