I just wouldn't consider a make do, that's all it is really, a make do.
Yes, let's admit that baths and sandpits and the like are basically a make do. But I don't think that means you can't have ducks.
We have four (was five
) runners in our orchard area, who have a dog bath for a pond (seconds quality - check Ebay). OK, it's not as big as I'd like it to be, but given the water needs to be changed every 1-2 days, I'd dread to think how disgusting even a reasonably sized permanent pond would become very quickly indeed.
I
have let ours out into the main pond on occasion (not often, because I feel sorry for the local newt population!), and yes they do love it. However, I still think they have a great life where they are. They're also a lot easier to keep in one place than chooks, as they don't tend to think of flying over obstacles or fences, so I reckon you could use a temporary fence to keep them out of any areas with seedlings etc. Oh, and they LOVE slugs!
As for the mess, yes they do stir up the mud a bit, but actually it's the bits I walk on, like by the gate that are by far the muddiest. As long as you don't try to keep too many in a small area, I still think you should be ok.