Just my two cents....
Did you or anyone check with a building inspector regarding the walkway, with only the top & lower rails?? I don't think that would fly here.
The additional 2x12 would be a lot more inexpensive a solution, and 'maybe' be required.
The PVC coated RGS is a great solution, but keep in mind it is $$$, and requires a dedicated bender.
Unistrut makes fiberglass and stainless strut FYI.
Schedule 80 PVC would be my choice, and I would seriously 'nudge' the 2x12s perhaps on both sides for appearance. (And it may make the insurance co. happy)
