From September 2014 to September 2015 it was Peter Dinklage who was the Ghost Voice, but Bungie couldn't afford him to voice the ghost more after a year so they needed a new Ghost Voice who is now Nolan North. My idea is that you could make The Ghost have different voices like Nolan North (Default) and many others, you could have other voice actors with different personalities and you could sell those ¨Voice Boxes¨ on Eververse. Nolan North's Ghost has a different Voice & Personality then Peter Dinklage had which I like, even though I love Peter Dinklage in Game of Thrones his Voice of The Ghost and Personality was oftently very dull and boring. Nolan North's Ghost has more Feelings & Personality and he says a lot of things that makes me chuckle. Some different voices and personalities would be awesome to change on your Ghost when you're doing missions, patrols etc.
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