Ayvah;
If there is any chance some dialogue could be voiced, why design the system to preclude that possibility?
As stated before, this problem has already been addressed in many other games including Bioware & Bethesda. I even remember a voiced line in one of the Bioware games -- the text had the character's name, but the voicejust said "Bhaalspawn" or something. Even if it can never be said verbally, I still like being allowed to choose.
(On the other hand, in a game like Witcher or Final Fantasy, I actually prefer not choosing, because the characters are already very strongly defined.)
A simple name substitution could cause issues with localizations, as well (masculine vs feminine names, maybe differences in grammar).
Localisation is tricky, but you definitely wouldn't be the first ones to face this challenge.