Do we have real understanding of how autistic people perceive things ??? It sound like one of the ideas for the game is to try to install understanding in the players about what it is to those who have that condition.
How many different flavors are there that might be expressed??
In 3D the 'focus' where what the player views shifts from attention getting overview to zooming in to some object/subset with exclusion of all else. Somehow the compulsive fascination would have to be expressed to hold focus on a narrow subject (perhaps with only faint whispers of all else that is going on).
I dont know if the person starts visualizing not just the immediate subject but all the myriad connections and associations/relations which expand into view in their brain ...
Most of the info about autism is taken from first-person account academic journals, so the explanation are rather vivid and arguably reliable. Moreover, autism isn't confined and predetermined through lists of behaviors; but a spectral disorder. I would then, limit the main character, let's say "A" to experience five symptoms throughout the game.
These symptoms would be triggered when the A is within a range of the specified area / physical objects / audio objects. For example, the player will experience blurry vision and tight, high-frequency sounds when he approached rumbling machines, etc.
I am still thinking to have narrative structures that would surface the character's autistic syndromes, not just on the game mechanics / gameplay itself ; a game that deals with psychological instability that would turn out to be the core antagonistic element of the gameplay. It would not be another typical indie horror, anyway.