There seems to be quite a bit of weirdness in perception here.
Applied to my mature forts, the split would yield a completely functional fort, and a completely dysfunctional fort. Even with several explicitly different "split mechanisms."
It isn't "Nobles stand" - they're only legendary in their own mind. Can you picture the US Congress shoved into a fort? They'd spend the next three years crafting lawsuits against one another and hamming it up for the observation camera.
If one says "Legendary for any reason, may only work in their field (or hauling the raw materials/results)", I get this split:
Fort One: Planters, brewers, butchers, weavers, dyers, clothiers, miners, woodcutters, herbalists, wood burners, furnace operators, lye/ash makers, metalsmiths, armorers, weaponsmiths, glassmakers, masons, engravers, tanners, leatherworkers, bonecrafters, stonecrafters, architect/manager/broker, mechanic, crossbowdwarves.
Fort two: Nobles, champions, cheese makers, soap makers, pump operators, siege engineers, animal trainers, animal husbandry, lever pullers, and random peasants.
Split two. You must become legendary the hard way, with artifacts just being sheer luck that should be discarded from consideration.
Fort Three: Planters, brewers, butchers, weavers, dyers, clothiers, miners, woodcutters, herbalists, wood burners, furnace operators, lye/ash makers, metalsmiths, armorers, weaponsmiths, glassmakers, masons, engravers, tanners, leatherworkers, bonecrafters, stonecrafters, architect/manager/broker, mechanic, crossbowdwarves.
Fort Four: Nobles, champions, cheese makers, soap makers, pump operators, siege engineers, animal trainers, animal husbandry, lever pullers, random peasants, and artificers. (Like three masons, ten stonecrafters, three bonecrafters, a weaponsmith, a maybe a jeweler.)
At least for my forts I'd be pretty happy continuing with the Galt-types. The hauling is the one key piece, but the key guys (planter, brewer, cook) are fast enough they can do their own hauling really. And there's no such thing as a Legendary Hauler - although it would be the first idiot to invent the wheelbarrow. (And I'd give him a tickertape parade myself.)
And actually butcher is actually quite easy if you embark somewhere that the goblins are going to be riding in on Beak Dogs. The first siege had me drafting six butchers and six tanners - and not clearing the backlog before the next siege. All legendaries in short order.