People are always asking which mission they need to complete in order to do a previous timed mission. I think it would be good if the message when they mouse-over the mission they can't do told them which mission they should do. For example, the want to do "Following the Trail," but when they go to the mission it would say, "You are not eligible for this mission. Complete Octafari Distress." That wording is just an example; it would probably need to make it more obvious that that might not be the only mission they need to complete.