Well, working on modifying the existing french version would be useless : in the french version, translaters forgave something vital. They just put accent like é, è, à, â, ô... but when there was an accent, the game showed a blank... well, here's an example of what I'm saying for the sentence "Follow your instructions to the letter"
In French, it must done : Suivez vos instructions à la lettre
But in fact, the game translated it by : Suivez vos instructions la lettre
So, if we take the existing traduction and modify it, we must modify too the texts.... A lot of work to get the same result.