Yes, rather easily.
What you want to tell FRED is this:
Every time the Orion receives an order to 'guard' something near the node (perhaps use a stationary fighter or an installation, as I believe nav buoys can't be guarded), clear the Orion's orders (via use of the clear-orders SEXP), then add an order for it to follow the waypoint path.
However there are a couple flaws with your system. First off, the attack order sucks with capital ships; it will lead to all sorts of ugly-looking maneuvering. Second, the Orion will always head for the first waypoint in the path every time it's ordered to guard the node.
Nonetheless, the above system should work.