I think the trick with vals is to get them large enough. A friend gave me 12"+ leopard vals that are holding out; the 3" corkscrews I ordered because I liked the way they looked had to be rescued for another tank. So far my goldfish has left anything ridiculously oversized (roughly twice her size) alone. She did eat or otherwise vaporize several crypts - again, always the smaller specimens. I do farm duckweed in all of my other tanks for her, which she gets about twice a week. I can't keep up with her appetite and it hasn't done anything to mitigate the destruction.
I believe a planted goldfish tank can be achieved ... with a lot of forethought and scheming.