I didn't have much time when I posted earlier, so I thought I better elaborate on why I thought that advice was bad...
Losing the cham and predatory cats are not even the biggest problems. The worst thing about that advice is that the chameleon will probably not have access to the things he needs most to survive: heat, UV, water and food.
Because of the term 'free-ranging', people tend to associate it with a
laissez-faire attitude to chameleon keeping: that the cham is essentially unrestricted in its movements.
But that couldn't be further from the truth. Free-range habitats are very controlled environments that require a lot of thought and planning. Good ones are probably even better thought out than conventional enclosures.
Even without the constraints of a cage, a chameleon still needs access to heat and UV light. So the lighting setup in a free range environment has to be very carefully planned, so that chams have easy access to the lighting, but also so they can't actually get to the lights and injure themselves.
They also need water, and you can easily imagine how much design has to go into creating a watering system that not only meets the chams' humidty and hydration needs, but also doesn't cause severe flooding and general swamp-like conditions: drainage systems in a free-range set up are far more complex than for most cages.
And finally, providing food for a cham in a free-range environment in a way that the cham can find the food and obtain necessary nutrition is also a challenge in really large spaces.
Free-ranging a cham is certainly not the easy option. On the contrary, free-ranging is definitely a choice that is better suited to those who are quite experienced in chameleon-keeping.
To the OP: the links posted earlier are going to be your best bet for a Melleri setup. I also have always like this idea (though I'm not sure it is suited to Meller's):
https://www.chameleonforums.com/open-air-enclosure-build-3076/
PS. I see the photos aren't available on that thread anymore. I'll see if I can PM SeanCJ and get him to upload them to this site. It was a really ambitious, but beautiful set-up.