I've heard of people using "bud vases", (you know the little push-on plastic tubes with water in them) on the very tips of their vanda's roots to keep them watered.
If that is so, why not simply hang the plant over some sort of water basin so that only the tips come in contact with the water?
The reason I'm asking is that I seem to recall seeing a picture from Malaysia where numerous vandas draped a riverbank with their roots.
It seems like an easy 'semi hydroponic' way to grow them... don't you think?