Well I can
half help here: I believe in 3.0 there's an option in the gui somewhere to change the commander keys. This implies that they're stored in a cvar. Sorry I don't know the cvar, but with steam's autocomplete maybe you could work it out. I'm pretty sure there's an option in the menu though. When I get home (I'm at work at the moment) I'll see if I can find that cvar for you.
Quick suggestion though, why not just make that config rebind your voice key to alt or something? Try adding this to ur autoexec.cfg, then just press \ to toggle between comm and normal. Might wanna add some echos in there and turn dev mode on or something (does that still work?)
alias bind_comm "unbind v; bind alt +voicerecord; bind \ bind_normal"
alias bind_normal "unbind alt; bind v +voicerecord; bind \ bind_comm"
bind_normal
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Edit: nvm, I googled a program to edit starcraft hotkeys

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