I grew up in Namibia, and we kept ALL our pets outside. The dogs had dog houses, the bunnies had a HUGE custom built picket fenced habitat complete with underground cement tunnels. The birds were in an aviary, the turtles lived on the back lawn that was gated so no dogs could get to them, and my mouse lived in the detached laundry room. The chickens roamed in a gigantic coop that was also a vegetable garden. We never lost an animal to weather or predators, and this was in Africa! So, I whole heartedly understand why the folks in Aus and NZL are talking of outdoor pigs. When my mom came to visit us last year she HOUNDED me over the "poor unfortunate piggies that I have in my living room", convinced that they would be happier outside where they can eat grass and watch birds. I told her they are "indoor pets" and that she had to let it go. We had many an argument over them. My argument that it was dangerous outside didn't stick because I couldn't produce one example of a pet we lost to living outdoors.
All that being said though, I LOVE having my pigs and bunny indoors. I like their noises, their quirks. I like chasing my bunny around the house and her licking my feet when I open the fridge. I like that I have a relationship with them, because try as you might, it's just not the same as visiting your outdoor pet, even if it is several times a day. So I would say indoors is the way to go!
Also, try not to obsess over grids. They are easy and plentiful here in the states, but they are not your ONLY option. Here is an opportunity to let our creative juices flow. We have a c&c, but we're putting together a see-through acrylic cage this summer, something that'll look much nicer in our new house. And we're building a large wood and chicken wire pen for us to put the animals in (separated for buns and pigs) in the lawn this summer when we are out there swimming and bbq'ing. So your building material options are unlimited.
Best of luck!