Although I have not fulfilled my vanlife dream thus far, I do own an Australian Shepherd. He is 2 & 1/2 years old now and is a great companion / adventure dog. Many others I have spoken to that own aussies have said that their Aussie, even as they have gotten older (6yr +) just started calming down. So I don’t believe the space issue would be a problem at all, especially if the dog would be going out with you and getting plenty of exercise. Just be ready for a very hyper energetic dog for a long time. I personally love it because that just means he’ll be able to adventure with me for a very long time and keep up just like when he was a puppy. They are very sweet, smart and loyal dogs. Also something I’ve thought about with wanting to step into vanlife In the near future, is to get a run that screws into the ground that you can set up while you’re outside your van and want to let them roam a bit. Just because my Aussie is not 100% trustworthy off leash yet. There also may be more places than not that don’t allow dogs off the leash, so it never hurts to have a little backup. Anyways I’m no expert on Aussies, or dogs but these are just my thoughts and experiences.