If you're going with speech, what does this do that you can't do with speech alone?
The value of keys is writing, supporting a composition and editing workflow.
Speech can do it all but eventually fatigue sets in if you do try to do it all with speech. Like RSI from too much typing but much faster. Best to use speech for the occasional long prose and steering, and something else for the yes/no/accept/decline options so the throat gets reasonable breaks.