Have you spoken to the speech pathologist about introducing sign language? Ours actually got us to use some signs which I was a bit surprised about, but it did work as a means to end in the big picture. I guess regardless of if we introduced signs or not our DD2 was making some of her own signs up anyway so that ship had sailed I should mention this was in a case where we knew there was a physical reason she wasn't able to form enough sounds to put together meaningful phrases, so that may have had an impact on why it was beneficial for us but may not be for everyone.