So, we dismantled it.
Replaced the rotten supports.
Put on smart new planks.
And replaced the original non-slip wire - my choice. I didn't want to send it unnecessary to the landfill though it was about six inches shorter than would have been ideal.
(Re)building bridges
Looks great! I assume that there's usually a creek there - at least earlier in the year? It looks dry now - another sign of the hot summer, I suppose. Good idea to reuse the wire (and it helps to keep people away from the edges of the bridge).