The easiest way to fix the autograph situation is to do like most other conventions do theirs. Have the autograph/photo times rotate and a strict limit placed on what is signed, with anything over it coming at an extra cost per item. This will keep lines moving at a very respectable pace. Otherwise, the cluster that happened this year will be your end result.
The same with getting badges. Just have 1 line feeding into the two registers. Much more efficient than having multiple lines extending into the middle of the room and having an obstacle course for everyone to walk through at busy times.
Also, vendors that have multiple pins of the same pin would benefit greatly from using one line instead of multiple lines. The number of plays and potential customers would greatly increase over the course of the weekend with this simple fix.