I searched for this on both the 'Eternal derpediderp voting thing' site and on the forums (To no avail.)
Now then, my suggestion will be short and concrete long and confusing:
Room templates.
The basic idea will be that when you have built a room (Or mined out an area.) you can use a 'template' option on that area (By marking with the mouse like when you build stockpiles) and a 'template' will be saved of that area.
My idea is that the 'template' is used sortof like a 'copy and paste' method to quickly create rooms.
Say you build a 12x12 room (Those nobles can go suck a dirty, blood-encrusted human male thong for all I care) with 1 bed, 2 chairs and 1 table in it.
Marking the whole room with the 'template' option on and saving it would allow you to later load that template, then click anywhere on the map and designations would automatically be made to mine, furnish and vomit in and make an exact copy of the other room.
This would be very useful when creating rooms as instead of manually having to tell the dwarves to mine, furnish and build the room, you would just be able to save an existing room template, load it and click a button (Rather than the mess that it kindof is right now, to be honest.)