I am saying that legally they would be required to stop an attraction (aside from those designed where they can't stop them), as it is a reasonable accommodation and ADA does specifically state that if a reasonable accommodation is requested and there is no other accommodation that could be provided to meet the guests needs, then they must comply with the request. Now for some guests slowing the attraction down may be sufficient, for others, such as those with service animals it would be dangerous to not stop the attraction and it would be reasonable to request that say Haunted Mansion be stopped to allow the guests to load. Yes, the cast members may not like it, but legally in some situations such as this they would be required to comply.