I'm not sure if this is what you were actually asking for, If you wanted a way of getting from Docklands to the Maribyrnong river without having to deal with the dangerous bike path on the Footscray Rd rail bridge, you can try this. Pretty much zero traffic.
You can also turn into Lloyd St from Arden St, and then follow the path alongside Dynon Rd to get to the Maribyrnong.. but the sight lines for motorists around the bridges over Lloyd St are poor, and probably wouldn't notice a bike on the road until it was too late.
(It's my usual way of getting to the western suburbs now as I
really don't like what they did to the bike path in and around the new rail bridge.. I usually arrive in this area from the Flemington end of the Capital City trail though, where this route isn't so much a diversion.)
If you were just wanting to add some picturesque k's to your existing commute, then the first thing that comes to mind is to ride around Port Melbourne/Albert Park
before you get to the Footscray Rd area. One good way is from the CBD, take the Sandridge Trail (following the lightrail line) to Station Pier, follow the coast around to Westgate Park, then onto Lorimer St and through Docklands. At the moment the southern part of the Westgate Park is closed because of the bridge strengthening works; instead you can go along another track in the park and arrive at the entrance to the Boeing carpark (there is some gravel over the disused train tracks there, check out Google Earth or nearmap.com to see where), and make your way down Sabre Dr to Lorimer St.
I was also going to suggest riding down to Williamstown, until I saw that's where you lived anyway..
You could follow the trail past Williamstown and out to Altona, that's pretty nice.
