Perhaps I can offer some insight. I've done, several quests for the Shadow, and Sunshine Squadrons. Only then was I am to say "I need a quest" and in return got permission to enter the winch, as for the lock that has supposedly been placed. I spent a good portion of yesterday exploring the winch in search of this lock, with the NPC server down I have nothing better to do except waste time proving or disproving theories and conjections. No lock was found. but I explored the fortress, and every builds door primarily. Im currently in search of a higher metallurgy trainer. I have not, checked the two towers in the Winch, or the fences. But why put them there? But as for access. You need a certain amount of Sunshine and Shadow Squadron quests completed. My quests that were completed were erased in the wipe, atleast the logs, and have no outside source to confirm how many quests I did for either. But I assure you it's atleast 8, 4 each.