I think a harness is a good idea to try and see how your cat is adjusting to it. I think I might give it a try too in the summer, but my little girl is quite scared and she doesn't want to explore my garden.
I would be so terrified to let them out of my sight, I don't think I could do it. My neighbour has a Bengal girl and she is out and about in our neighbourhood, and I've seen her getting up to so many naughty things
, bullying dogs, fighting with other cats, and she wanders off quite far away, so I wouldn't let my baby out, too many dangers out there. Or maybe I am just too overprotective.