Since the Haunted Mansion is operated on an Omnimover the lines should be moving efficiently but one thing in particular slows things down and could be responsible for the long lines that this ride has and that is the preshow elevator, where only a small amount of people can board at a time and then the elevator must be brought back up to bring more people on.
Now suppose that instead of an elevator you just have stairs. Do you think that losing the preshow and replacing it with stairs leading to the loading belt that the line for the ride would move a little faster and thus shorten wait times? Do you think that option should be available for those who want to get on the ride quickly and don't want to do the preshow? Are the line problems at Haunted Mansion major enough to warrant it?