I have largely gone to wood baskets for all my big Catts (those too large to mount). Roots do grow into and around the slats of the basket (think of it as a 3-dimensional mount.) Some of the roots do escape anyway. I like your "stalactite" analogy.
If you get the roots nice and soft with a good soaking, you can likely wrap them around inside the basket, controlling them for at least a little while. Don't worry too much about media - some large bark maybe. They tend to grow to the outside of the basket, somewhat ignoring the media.