I know how you feel, trust me, I'm a sound guy first, modder second. The recorded voice, no matter the tools at one's disposal, is still the most important part. To say otherwise goes against the GOOD rule of recording. They need to get the character and all their inflections just right and in character, and still manage to sound as close to the same. Obviously, a formant-controlling pitch shift software (like Melodyne) would help a ton, but utilizing that would require a great deal of work to get it sounding right AND natural enough, and then you would need a good EQ Match tool or plugin (I'm thinking about getting the full iZotope Ozone Mastering Bundle, it has one) that could change the sound to very closely match the frequency curve of another file.
The only time something like this sounds like a good idea is if you're just worried about one character, because you get to know that character's voice inside and out in such a way that you can use the formant-controlling pitch shift software as easily as a simple compressor. The downside to this: you will very likely be fed up with this character's voice by the time you're done, if you last that long.