I don't much like the way legendary status works right now. I've actually started to reduce my specialization so that I don't end up with two legendary carpenters/masons/bonecarvers/cooks/brewers/etc. after a couple years, because it bothers me that a legendary worker can produce more goods of a higher quality that four mediocre ones. I can see the beds being better, or getting made faster, but not both.
How about this: A worker, under normal circumstances, can use his ability to fill orders faster and better, but there's a cap on quality, at "Finely Crafted". If you want to make superior, exceptional or masterful works, then the job has to be submitted to a master crafter, and just having a lot of XP isn't enough. In order to make a citizen into a "Master Mason" and get those great doors, you have to find a guy who's skill is at least "Great" and promote him to the role, like a Sheriff. Once he's got the sash on, he needs to have a workshop that only he is allowed to use, a study, and a cabinet (just off the top of my head). The master's shop will not queue tasks from the task manager, you have to specifically request that he do the job, and jobs from the master's shop take way longer than a normal shop, like ten times as long. As he skills up, he'll be more likely to produce the exceptional or masterful works, but his pace will not improve. Additionally, his skill-ups will cause him to undergo promotions, so he'll require a fancier study, maybe some more furniture or a private dining room to keep him happy. Once you have a level 20 omega-carpenter, he'll need quarters rivaling the Hammerer's, with a tomb and a sweet bedroom and the whole nine yards.
That way, you can train up an assembly line that can pound out +Obsidian Throne+s like clockwork, but a better piece of work will require an expert in a more personalized environment, and it'll take more than some decent booze and a waterfall to keep him ecstatic. An added benefit of this would be the ability to custom-order a "good" item, separate from the industrial machine of the fort, and that one fancy coffin will be produced promptly and well.