Can you please suggest some good articles, research or data to support having a TOD in a classroom with a 5 year old with significant delays “across the board” (the student has bilateral CIs, no sign language, extreme speech delays [apraxia?])?
Given the huge individual differences among deaf children with multiple challenges, this is an impossible question to answer. You really are (or should be) looking for information relevant to a very specific child, and we don’t have much to go on. How significant are the delays? Is the child using the CIs successfully? What is the cause of the extreme speech delays? Has there been an assessment that suggests apraxia or is that a guess, and if the latter, based on what? Does the child not use sign language because s/he has not responded to it or because s/he has not been exposed to it?
You can find articles and chapters about the educational needs of deaf children with additional disabilities (see below), but you really want to know why that 5year-old should have a teacher of the deaf. You will not get that from an article. You are going to need a comprehensive evaluation done by people who know what they are doing and can communicate effectively with the child. There is no one right answer; it depends on the needs of each child.
Mauk, G. W. & Mauk, P. P. (1998). Considerations, conceptualizations, and challenges in the study of concomitant learning disabilities among children and adolescents who are deaf or hard of hearing. Journal of Deaf Studies and Deaf Education, 3, 15-34.
Vreeland, J. (2014). Educating deaf children with multiple challenges.