The cage dimension of 16.5" may be a bit narrow, but otherwise the cage size is OK. I use zip ties all the time...great invention! You may find you want more foliage depending on how the Ficus fits in the space. Another good bushy plant is Hawaiian schefflera. It is often sold at Home Depot or other plant nurseries as "tropical foliage". Pothos is also good, you can set the pot on a pedestal or hang it from the cage frame. Instead of dowels you could use scrubbed natural barked branches from a tree. Scrub them down with a bleach/water solution (1 part bleach 9 parts hot water), rinse until you don't smell bleach, let them dry thoroughly. It will look a bit more "natural" and help keep the cham's claw tips from being as sharp. Use different sizes, some larger diameter than the cham's grip, some smaller to exercise the feet and help keep old sheds from building up. Use metal mesh on the cage top if you plan on setting lights on top. Check the following links for pics of setups:
http://www.adcham.com
http://www.chameleonnews.com
http://www.chameleonjournals.com
One of the more frustrating parts of cham cages is what to use for the bottom. Some ideas include plastic sweater boxes, plastic drip pans from refrigerators, cement tray forms, hydroponics flood trays, dog crate pans, or make one to size by gluing plastic panels together.