I'll personally vouch for SHIV speech. It's not a mod but a standalone program so if you don't like it you can simply delete it without touching anything within your SHIV folders etc.
I find it an excellent immersion tool and don't play without it. It's pretty cool to say "Take her down" and have the crew react with "Set dive planes for normal dive...." etc
It does emulate keystrokes so you will see the cursor move around sometimes but that's a minor distraction. Overall it's a great addition for a free program.
