I used to raise ficus bonsai, still have a couple. They need to be able to dry out every once in a while and will rot if they are kept constantly wet. I had luck with a ficus planted in a wall pocket in my viv that could dry out every so often. Lasted 4 years until my creeping ficus killed it.
I have more than a dozen species of ficus...a few as bonsai...but none in a viv. Some of mine stay constantly moist...but they are either mounted on a rock or have their root crown 5 or so inches above soil level.
In a viv I'd recommend growing a Ficus as an epiphyte...especially on a horizontal and/or smooth branch. That way it will have excellent drainage and you'll be able to easily trim the roots. Depending on how moist you keep your viv, you might need to use some Sphagnum moss to help the Ficus establish.
Yesterday I picked up a nice Ficus diversifolia from Kartuz Greenhouse. I plan on growing it as an epiphyte in my tree.