Two quick questions, if I may: Is the JSON extensible via another mod? And would it be any work to add an optional sound argument, as I'm also using voice actors?
A "character" (personality) definition .json can't be partially modified, only overwritten (which AFAIK requires the mod in question to load after Combat Chatter, so BSG can't do it). New character definitions can be created and referenced in the .csv file (SS will merge copies from different mods), although I don't actually have support for using custom personalities yet.
For sound, you'd have to change the strings for each line to a JSONObject (with one key-value pair for the text and another for the sound), then modify the
loader and
character definition class accordingly. I'll probably implement this in a later version, but that won't be coming anytime soon I'm afraid.
If it makes things easier for you, feel free to copy
the repo's code into your mod and modify it

(just credit me in a comment header or somesuch for now, I'll probably put later versions of this mod under the MIT license)