Alright. I looked through the last 5 pages of threads, and couldn't find anything talking about this. I'm sorry for the rant, but I'm severely pissed off.
Please, someone, tell me why you are allowed to sell your Thieves Guild Armor if it's technically a QUEST ITEM?! I just became the Thieves Guild Master, I'm well over 100 hours into the game, and I cannot unlock the achievement for "Returning the Thieves Guild to its former glory" because I cannot re-acquire the Guild Armor necessary to turn into Tonila.
Why in the hell would you make it so I can sell it if its obviously necessary to completing one of the 4 main guild quests?!
I really love this game, but if you seriously expect me to fully replay through it just to keep the armor you've got to be joking.
Please, for the love of God and all great things in Skyrim, release a DLC where you can, by some way, re-acquire the Thieves Guild Armor. This is a glaring issue that has screwed up a lot of people's playthroughs. I pride myself in getting every achievement in one playthrough (did it with Oblivion, would really love to do it with Skyrim) but this is just a joke.
Again, sorry if this has already been posted, and sorry for the bad language in the rant, but I cannot believe I just spent the past 3 weeks doing Thieves Guild quests from Delvin and Vex, have just become the Thieves Guild Master, and am now required to turn in armor that I do not have and cannot obtain again. Moreover, I cannot believe these past 100 hours have been spent so I can only obtain 970/1000 achievement points. At least the players on PC can download a mod to gain the armor again. Us 360 and PS3 owners are screwed.
While I feel your pain, I cannot support the effort to tag yet more items as quest items. The game needs more consequences for your actions, not fewer. Unfortunately, you are now feeling the consequences for your decision to sell your Thieves Guild Armor. Why did you do that when they give you a bed and end table to put your stuff in at the guild? Did you need the coin that badly?
You joined a guild that was down on its luck and of obvious limited resources. They trusted you with a really awesome set of light thieves armor that was given to you so you could assist in rebuilding the guild to its former glory and you just up and sold it? That kind of action in an RPG deserves some serious consequences and while I really do feel bad for what happened to you, I can in no way support your position.
I had a similar experience with my Khajiit Thief/Assission, who, without thinking too critically about the decision, took the broken Asura star to the wrong person for fixing and now is stuck with the white version fo the star when the black version would be so much better for that character. What can I say? I was three in the morning and I was really tired and just wanted to finish the quest, and it was not until quite some time later that I realized the mistake. Now I have to live with that for the rest of time I play the character, but that is part of an RPG. Living with the consequences of bad decisions.
Honestly, I wish there were more decisions like this in the game that had far reaching consequences, then Skyrim would be a true RPG, and not just an action game with RPG elements.