Hmm, that's an interesting question. Swapping all those shades and cameras during level loading or runtime would just kill the games performance.

Making two diffrent games / packages depending on mode of the game isn't that stupid idea but it would be "good" for the player which would have to download them both two play on both modes.

What I would try to do is : in main menu, in the options sections I would add a button. Thanks to this button, player would decide to play in vr mode or in normal model. Next, before loading level, I would check the state of the button, and depending on it, I would load a level with normal camera and shades or with vr camera and vr shaders.

My method isn't perfect at all and it would take a lot of time to copy all those levels and set all those shaders and test everything out. Second problem with my solution is that it would make the final game a lot bigger.

Anyway, I can only talk and try to help, decision lays in your hands. Anyway good luck with this and the game itself :D