Duplicate shops are necessary for diverse lavor. Animals cant be sheared at the agriculture farmers workshop they need their own. The dwarf in charge of garbage can have a bone carver crafts dwarf workshop.
That is the ultimate goal, the problem is that the rules forbid it in a catch-22 style.
1) No community property, all workshops must be owned.
2) Only notables can own land or industries
3) To be notable, dwarves must be both dwarfed AND legendary, unless they are a noble, or a member of the starting 7.
4) (hinted at strongly, but not overtly stated) Notables should really only own a single industry
This means that these new migrants with less than legendary status, that aren't dwarfed, cant own property on which to have workshops to build their skills.
Chicken and egg.
I can circumvent this somewhat by temporarily assigning duties at workshops that are owned inside existing landowners' properties, intended for other industries, until they can get their legendary statuses, and we can attract observers that want dwarfed dwarves. At that point, they will meet the criteria for owning a modest property and having an industry.
The problem is getting industries that have no "legal" means of being started, started.
Since my character is built around a shameless tax-dodger, rule breaker, and general ne'er-do-well being put into an administrative position, his doing this kind of "legal gymnastics" to get things running is, IMO, perfectly in line. I however *AM* trying my best to stay as "In the rules" as is possible.
Ideally, the goal is to have redundant workshops, in appropriately zoned and owned localities. But Rome wasn't built in a day, and I have to play with the rules as written.