Absolutely...the keys are that the cage must be HUGE, and very heavily planted--as a result, strong lighting is key, and of course it must be UVB lighting. You have to create a temperature gradient that's proper without scorching the plants, and select non-toxic plants that can survive in that environment.
I recommend using computer fans or an air pump or two to create good air circulation in the cage or tank (don't consider anything under 100 gallons for what he's proposing, and much bigger would be better). Mold is a huge enemy.
It has to be just about packed with greenery. Be sure that the water has a high quality filtration system, perhaps blocked from direct access so that nothing can get stuck in the intake. Be sure that the water has plenty of places where creatures can easily climb out--a small lizard could quickly drown.
Set it all up, plants, lights, heat, filtration, perhaps some water plants, snails, a guppy or two....
And run it as a terrarium for at least 6 months. That will allow you to determine if you're going to have any problems! You can adjust to make sure you can keep your plants alive, that mold isn't growing...you can establish some species of moss on driftwood, get your water cycled properly, and get yourself a little mini-ecosystem that actually works, BEFORE you add animals to complicate the picture.
Then, you start out small. First, as has been pointed out, most small lizards are going to be WC. That means several months of quarantine for each and every one of them, and vet checks to clear them of parasites. You want them clean, completely healthy, and thriving before you put them in your expensive big setup.
One animal with parasites could result in all the animals being infested, all dying...and then you'd have to rip the whole thing down and sterilize every inch of it, throwing away what couldn't be sterilized. NOT a pretty prospect.
You HAVE to be sure the animals going into the community cage are parasite-free and completely healthy.
You can, if you hunt around, possibly find what you are looking for as captive-breds. Quarantine them, and after 4 months, add them to the tank. Do only 1 species at a time. Start with the less aggressive species first. Be very aware of possible conflicts. Dart frogs are cute...they're also small and resemble food, and if licked, can kill. Not a good choice.
Fire-bellied toads...an iffy prospect. Also secrete toxins. Newts secrete toxins. Green or grey tree frogs might work out well.
House geckos and mediterranean geckos (similar size and appearance) can work out well. Green, brown, and bark anoles can do well, as can the long-tailed grass lizards.
I saw a community setup with a green grass snake in it, but I'd be leery of that.
Do not overcrowd. You cannot pack a lot of animals into a community tank, and expect it to work. A 100 gallon tank, heavily planted, you can probably get away with a tree frog, a couple of anoles, a couple of house geckos, some guppies, maybe tiny ground skink or two...and that's it.
I would be concerned about a hermit crab's well being in such a setup, and also concerned that it might pose a threat to the other animals.
I once saw a room-sized community setup that contained a variety of arboreal lizards, box turtles, painted turtles, white's tree frogs, and java sparrows. The birds were nesting. The trees and shrubs, vines on the walls, and actual hide boxes kept everyone secure--the animals all appeared to be doing well.
It can be done, and the effect is really cool, but you have to be careful, thorough, and shell out the bucks. The room-sized enclosure was lit by halogens, for the UVB.
Hopefully that will happen fo rus when we try this oneday.