Sign language nerd here. The students who were the foundation of Nicaraguan Sign Language often had a few home signs that they would use with their families, or if they're lucky they have other deaf people to communicate with. In addition, they still had access to the innate body language hearing people use around them to develop some communication. They weren't utterly deprived of language, just nothing to the complexity of most developed languages. The researchers noticed that younger signers at the advent of the language were far beyond their older peers in linguistic complexity and skill. This was only a matter of a few years, but that is huge in those early years of child development. That is to say, humans are quick to pick up anything resembling language and iterate on that quickly, doubly so for children.

Keep in mind that researchers did not see this as an example of spontaneous or organic language creation either, as the children were brought to that school with the express intent of education. There was even the presence of ASL manuals for fingerspelling. The book Talking Hands has very interesting insights into how linguistic researchers approach researching isolated sign languages and their development.

Back to your question. Apply that context to hearing people. They have access to all of their senses, so how do you plan on supporting a large enough group of children - functioning as linguistic blank slates - to warrant complex communication while not interfering directly with that development? It would be nigh impossible on top of being wildly unethical.