Hi Edwin,
Actualy that is a subject very near and dear to me, as it keeps with the whole concept of "reef" keeping. Anyone can keep a bunch of corals sitting on top of some rocks, but is that a reef? Not really, since the word "reef" includes thousands upon thousands of species that are not corals. This is the same goal that I have for my system and why it is set up in the manner that it is. From a refugium filled with live rock and macro algae to the DSB, all of which provides the various habitats that function (or should) together to make life possible for the corals, with as little equipment and/or intervention on my part. Letting the "reef" act as it would in nature.
Your best chance of providing or getting the cryptic species (sponges, tunicates, worms, clams and so on) are by simply collecting live rock that was in a cryptic zone on the reef. I say that simply because most all of the species that make such zones their home do not transfer well and are about all but impossible to remove from a rock and then establish it again without killing it. It is much better to get such things already on/in a rock with as little disturbance to the individual species as possible.
Such a cryptic zone is easily created and most every tank already has it by simply having a live rock landscape, but for what you and I have in mind, the landscaping of the rocks should not be so much of a vertical narrow wall but more of a "mountain" that is stacked in such a way that allows for a lot of mini dark caves that can get some good water flow. That flow is extremely important for such species.
The other issue that comes with keeping species such as the sponges and tunicates is that they need extremely small food, both bacterial and particulates, when I say small, I mean VERY small. They also need a great deal of such foods and is something that we have a very hard time providing. That and sponges and tunicates are extremely efficient at gathering food and can quickly deplete what our systems can provide, which then limits our ability to keep them alive over the long term.
Another issue is the species themselves. Some species will do much better in a system than others and will become dominant simply because they have what they need. That "need" being provided by the tank is most often unique to just that one tank. My system might have a great deal of one species of sponge or tunicates, yet if I gave you some, your system most likely would not support them. Which is why I suggest a great many cryptic live rocks as you can get so that you have a better chance of getting a species or a few species that find your tank suitable.
In fact, tomorrow I will be doing some diving to collect some corals as well as looking for suitable reef sponges and some deep water live rock for my refugium to do and attempt to do, exactly what you have in mind.
Chuck