I think it would be interesting to add some more languages only certain groups can speak, like a combinatio n pf light and sound for Kidan that have the glow organ. If they don't have the organ, but choosen the language, they could at least understand it. Think some sign-only language might be too problematic as you would be able to communicate while being deafened. Some languages i did think of:
Glowtin, Kidan: Combined use of light and sound signals to be able to relay information faster. Used by the sub-species of Kidan that have the needed glow organ.
Siik'Maas, Tajaran: Basically Bay's Siik'Tajr, our Siik'Tajr does equal Bay's Siik'Maas.
Rootsong, Diona: Rootspeak combined with flowery aroma. Used by Dionas that decided to settle on a planet rather than becoming a big gestalt in space.
Compressed Datastream, IPC: Using the TV-like head to display data while also sending Trinary signal for re-combination with the visual data for decompression. Utilised from the older IPC models, designed as it needed less talk, and such, more work done with the same communication.
Vox Apgin, Vox: Vox utilising a short range telepathic communication, origin of that would be the vox apex, besides using normal shrieking. Came from vox that wanted to have some more secure talk to the other members of the vox.
I figure you could give every race such a semi-vocal language, would just need some lore fluff around, more precisely why it would have happened in the first place.
I would at least like to see some semi-vocal languages, the system for them would already be in place, so why not use it?