I've been throwing this around as well
I've got it down to either another Yorkie, a Biewer (I am trying to move to Germany after all
) a French Bulldog, a Papillion, or a Chi. I'm afraid that a chi wouldn't be able to handle Rizzo's rough play as they seem to come in mostly small packages, I like the idea ofa Papillion because they're so pretty, and they're built about how Rizzo is now and many lists classify them as the smartest of the small dog breeds (but I know better, haha) just means that they're easier to train than say a Yorkie
I love French Bulldogs, they're beautiful and so full of spunk but I think the size may be too much for Rizzo. The only one we've run into before was a poorly trained female, but Rizzo loved to taunt and run since she couldn't keep up, lol. And a Biewer or Yorkie, for obvious reasons, I love this breed and would love to have a Biewer since they are so pretty
Good luck with your decision, its a tough one that I keep going back and forth on.