If your new tank is half screen you won't need the fan.
I've bred several species in the past in large glass aquaria and they were very healthy and happy. There are other forum members who have done the same or who have used the new tanks with the ventilation panel near the bottom front of the tank in addition to the top.
Like Flux said - we've had several customers who keep chameleons in large, all-glass enclosures without problems. For the really sensitive species, or in exceptionally dry areas, it seems to help keep humidity within a tolerable range for the chameleon.
However, for large, sturdier species, housing them in screen cages allows for a less expensive option for larger caging, again as FluxLizard said. Reptarium screen cages work well for large outdoor enclosures that are easy to clean, or you can use the aluminum screen cages most commonly available for chameleons.
In the stores, indoors our chameleons are housed in half screen, half glass cages, and they all do well in that setup. During good weather, many of them are placed outdoors in larger reptarium cages, and again they do well. The nice thing about the outdoor Reptariums is that it is easy to put the hose on a mist setting and really thoroughly mist the chams several times a day. And on the flip side, the indoor cages look very nice for display, and do help with keeping humidity and warmth within the cage in a nice balance without the air becoming too stagnant.
It's worth trying the half acrylic cage, for an animal as beautiful as a panther chameleon, having even just one panel that's clear material will make for a nice display at the very least.
-Jen