I would suggest that the problem is that there are so many potential areas which can cause problems, but which do not affect all people on the spectrum, which is the difficulty.
Some examples:
Some cannot stand loud music, others don't mind.
Some cannot stand sirens (or other sounds), others don't mind.
Some cannot stand bright lights, others don't mind.
Different quantities of people affect each of us differently (and can be dependant on situation: Outdoors, in a large area, or in a small shop/room)
Different smells affect us all differently (some like smells that others want to get as far from as possible).
And if you were to have details for each of these items, how would they be measured, and who would be measuring these (particularly as many are not "constant", instead varying in intensity over time)?
Plus, would you want to go through the process of finding your specific limits for any/all areas for which any one person on the spectrum had an issue, particularly if you were extremely sensitive to any of them - or force others to endure the same? Not to mention (for the tin-foil hat brigade) what could happen if the "wrong" people got this information...