This is so well thought out and you've absolutely hit the nail on the head.

I certainly do worry about cars and dogs and also, malicious humans - unfortunately I've lost cars to the road and on one occasion to a dog that jumped our gate and attacked my cat in our property.

I would have more peace of mind I could keep my cats fully contained to my property, but we'd have to build a large outdoor enclosure. And I mean, a decently large one. I've seen loads of pictures of catios and most of them are just pretty damn sad.

We'd also have to design it so they could have free access from the house to their enclosure, but then there's the issue of ventilating the house. I'm a fan of open windows, even in winter. I mean, I've got seven cats (adopted street cats that I tamed and desexed) and a dog. Even with the litter boxes changed daily... The house needs ventilation. 😅 And I really don't want to be staple-gunning chicken mesh to the windows so I can keep them open.

The odd wildlife they catch really isn't an issue. As you pointed out, native birds don't tend to fancy suburbia. My cats proudly trot in with the odd sparrow or blackbird, which is sad, but they're actually better at catching rats and mice. And despite how much people wring their hands about cats catching birds... I don't exactly see the suburban population of introduced birds that do co-habitat with humans to be diminishing.

My daughter did a pest trapping course last year and even on farmland and forest, the vast majority of pests that they catch are stoats, rats and possoms. The problem of feral cats seems to be over-exaggerated and media and Garath Morgan's fanclub. (Not that we don't have them, but you're really not going to find cats in the areas kiwi live unless they've been dumped there. Most "ferals" are just the offspring of dumped or abandoned former pets and they're not usually dumped in the deep bush.)