Hmm. I see your points but yeah I guess it just doesn't apply in my situation.
We don't leave doors open here (AC gets out, critters get in). And yeah our place is different being in florida with a yard that's different from uk yards. We've got a lot of wild animals in our yard and being big it's not secure and safe. It was ok for our bridge lab to be off leash in daytime while we were around but not for the small dogs who are more vulnerable to predators etc etc.
It's always just worked for us to go on walks and the lab went to the backyard to pee while the yorkies and maltese go to the front yard.
I've been wanting to get my own dogs for ages, I'm particularly interested in northern/spitz breeds like american eskimo, husky, shiba, etc
I don't really think about the what ifs of it - we didn't when we got our other dogs.
I just don't think it's a good idea to rely on the dog being ok with the rabbits. If you have to rely on them co-inhabiting then what happens if things change and they won't? I still feel a barrier would be best in this situation, especially at first. You only need inches for that - it can be super close to the rabbit's accommodation.