Of course diplomacy players will have to live with the regular sounded envoy and pact announcements.
If you want email me the diplomacy files and I'll convert them as well and put them in the mod. (I never bothered buying the diplomacy expansion given I do MP games 90% of the time making it somewhat useless to me.)
Also including the original sound files to uninstall is unnecessary, you can just delete the folder or disable the mod.
In my readme file I included instructions on how to overwrite the core game files themselves with the new voices (letting it be "always on" and people won't need to mess around integrating it into other mods they like.)
The uninstall files were to make it easier for people who go this route to re-overwrite the modded files with the originals without having to first fuss with making a back up copy of the sound directory (which is around 265mb) or reinstalling the game.
Hmm... I personally don't like the flattening effect of using a pitch reduction without compensating for it in some way, such as dynamics processing or EQ. I think this was a pretty simple batch process, though(?) - if you wanted to min-max you'd have to set up a specific batch for each averaging pitch set.
Indeed, I'll be the first to admit this is a "quick'n dirty" voice mod I spent about an hour or so on. If I had a decent audio morphing program I'd be happy to put more effort into making a higher quality version. Unfortunately the free/cheap programs are pretty limited/lousy in their capability and I don't have the $90-$300+ to dump into Adobe Audition any time in the foreseeable future.