Or the protection could be purely mechanical, based on the proximity of the prism. In which case the party would be protected by Orpheus, but you would not need to interact with him, and the only choice you make towards the end is whether to free him, or not. Of course, this would mean there would be no "someone has to turn into a mind flayer" plot twist, but frankly that would be a bonus.
You could basically mod out all the dream scenes with the Emperor and the story would remain intact for the most part with the prism simply being an artifact that shields from illithid influences. The only thing that would probably need a rewrite is the Gith creché scene and the final dilemma.
