I made a catch-all gumbo over the weekend, using chorizo in place of andouille, dried okra from the spice store in the place of fresh, and the stock I'd made for lasagne in brodo the other night. All the substitutions worked out fine. The big lesson was to warm the stock before adding to the roux-vegetable mix. It resulted in a silkier, thicker gumbo, with less skimming (and thus more fat) and actually a good thickness to it. Cold stock apparently shocks the roux into separating. I'll check my McGee book tonight for the science on this.