I actually got the 70L pot and the copper element you linked from Craftbrewer in your OP for my BIAB setup.
It seems to work fine but I don't exactly get a vigorous boil I'm afraid.
When it comes to protecting the bag from the element while the element is on, I spoke to Ross about it initially and he mentioned that it's probably unlikely that the element would get hot enough to melt the bag when it's in liquid. But just to make sure, I make do by pegging the bag to the other side of the pot if I need to turn the element on.