If and only if you get the magical combination that works out for what you need. Otherwise it's just another skill you have to grind up before getting consistent high quality. I personally foresee a lot of migrants like glass armorers and leather carpenters.
Now that's just being obtuse, those combinations wouldn't even exist in the RNG for a start. Unless Toady One was an idiot, and we KNOW that's not the case. A computer program can tabulate only allowed possibilities very easily. Also, rates of skill gain can be tweaked, and ALL relevant skills to a job cross-train simultaneously. There's no need to assume they're being serially trained.
But even if the game somehow
did generate skill-set like that, a glass armourer is 50% to being any type of armourer, a leather carpenter only needs to buff his "wood" skill to be making wooden furniture.
And you're not considering how matrix skills systems work :-
Materials
Stone
Metal
Wood
Bone
Process
Builder
Crafter
Carver
^ 7 Skills total above, gives a max. of 12 combinations. not ALL of these have to be generated :-
Mason (Job) = Stone + Builder
Stonecrafter = Stone + Crafter
Stone Detailer = Stone + Carver
Carpenter = Wood + Builder
Woodcrafter = Wood + Crafter
Wood Carver = Wood + Carver Not Existing in Dwarf Fortress (Yet)
Blacksmith = Metal + Builder
Metalcrafter = Metal + Crafter
Engraver(Metal) = Metal + Carver Not Existing in Dwarf Fortress (Yet)
Bone Carver = Bone + Carver
(Another 2 potential "Bone" combinations. These combinations would never actual be referenced by a job in-game.)
On "Table 2" I've listed the existing professions on the left, and the "breakdown" on the right.
That's 8
existing Dwarf Fortress jobs I've got through already, using 7 skills in Table 1, and the total skill rate gains can be tweaked to match, or exceed the current rate of gain in the game, so there's no logical reason to assume it would take longer to buff these skills. It could be instant as far as the game is concerned. There's also some "unused" combinations which no job in DF currently uses. Some make sense, some not so much.
To say every combination somehow *must* appear makes no more sense than lamenting that you might get fish-cleaner/alchemists or lye-maker/pump-operators.
Seeing as how I can create the exact same list of professions of current Dwarf Fortress on the left, that is what the game can "generate", and auto-magically give the Dwarf the "breakdown" skills needed. So no "glass armourer's" etc, that is an unecessary artifact, not part of this system.
but now there's interlinks between the jobs, both in Materials knowledge, and Process knowledge. Also, having a part-skill gives a boost to ALL related areas, eg having any "stone" skill gives you a boost to doing / learning all the stone jobs. Same with the other materials. Having any "Crafter" skill aids in "crafting" any material. A hypothetical woodcarver would get a starting advantage in both working with wood in ALL contexts but also has ability to learn carving on ANY material. So he'd be trainable to existing related jobs even if he existed but his particular skill combo was not actually implemented in the game.
So a hypothetical glass armourer would NOT be limited to "glass armour". you're not even thinking this through.
He'd be good at ANYTHING GLASS or ANYTHING ARMOUR. Any anyway, a simple job look-up table would mean you only get combinations the game actually uses.
So, effectively, matrix skill structure can mimic the EXACT same professions we have now, but with added skill interlinks. Also, there can
still be jobs in the table that use only 1 skill, or 3 skills etc. So those "odd" jobs which don't fit into a "process x material" system don't need to be forced to fit, they can be exceptions or follow their own logic. Other subsets of job skills can even have their own matrix's based on any logical breakdown, or entirely left the way they are now.
e.g. Mining can still be only 1 skill even if others are using the matrix style.
