I can personally say that I was building the Elite Panel system (polymer walls), but switched to Structural Armor last year. Polymer doesn't hold up like it used to, and steel WILL rust.. could cause a lot of issues in the future. That's why I stick with the fiber-reinforced composite wall system (Structural Armor or Fuzion 5010). And you are correct when saying the bracing will rust, but it's backfilled and never really seen again. All the other components are non-corrosive and as strong as steel.. have you seen any of the videos?
In regards to pumps and filters.. to be honest.. there are a