Not sure if this was suggested by someone previously and I apologize because I'm being pressured to share via an FC mate who I just gave this idea to lol. Typically I don't camp the forums nor do i typically worry about the housing system because to me it's completely useless and I would like to see more relevant features added to make them more appealing. I apologize if this offends as I know some people enjoy the housing system, but I do not at this time and it just feels like a redundant method to keep people subscribed.
Anyway, my idea is one of convenience. We currently have NPC vendors and the like at our houses and my idea uses a similar concept. Crafting NPCs basically. Allow players to hire NPCs that would do crafts for them so that players can choose to either craft the items themselves or let the NPC handle it. To prevent misuse of the feature however the NPCs would be restricted in what they can craft. My ideas for this is primarily a restriction system similar to retainers where their highest level is the highest level you have obtained in that same class/job. In this case these NPCs would not be able to craft anything you cannot craft yourself. This would be like quick synthesis because you cannot use that feature unless you've crafted the item before, though in this case you simply need to be high enough level to craft it for the NPC to craft it for you. Other restrictions can also be put into place as well such as not allowing the NPC to do master crafts or something that way it doesn't feel like a replacement to DoH classes. To further add to this so that it would have minimal impact on the economy in game is that these NPCs will not craft the items immediately either. Instead they will have a timer for how long it takes to craft said item, this will take some balancing to get a good fit because we want a trade off between time commitment and convenience here. Crafting the item yourself will always be much faster so that players can't just mass produce at an NPC while they go off adventuring and risk flooding the market with too many items, however crafting the items yourself would require you commit some time to that which would otherwise go to adventuring.
Basically how it would work is you simply go up to the NPC and they open a shop window with options, you select the craft you want to do and the NPC will take all the relevant items from your inventory. You can choose to use HQ items as well if you'd like as there would be a set chance for an item to finish as an HQ item and using certain HQ materials can increase that chance slightly. This may result in a higher chance for an HQ item from this feature than quick synthesis with this method however. Also to make it more interactive changes can be made to some of the furniture items that gave DoH bonuses in the past so that they can also provide bonuses to this NPC as well for their crafts.