However, I wonder if a derived class might ...

So I'm thinking why not just provide the order already?

I wouldn't add it. I try to avoid adding features that don't pay off immediately. It keeps my code smaller and cleaner, helps me hit release dates earlier, and prevents me from taking risks that don't pay off.

If you wait until you actually need it, you'll be in a better position to design a good API. You'll also have a better idea what performance level you need to hit.