I think you'd spend more energy trying to patch pieces in than you would just removing it. It's easy to get to. I would just remove the whole rusted out piece and replace the whole thing with new.
Or, if you're not necessarily trying to "restore" the rig, I replaced mine with 2x2x.120 HREW which is part of my slider and cage support. It's not necessarily a huge gain in strength, but it won't buckle like the 16 gauge would under a heavy load.