I think it's a great idea to start over,
and I experienced so much the difference between 2b and 6.2,
so I know what you're talking about.
First MW was all about testing, and in the end Dwarves had almost everything (a lot of structures),
then the others had "specific structures to make them special".
Now you're planning to do it "from scratch", so new Dwarves will have what they need to have.
In my opinion Guilds and special a few "specialization" structures are Humans stuff.
I don't have particular suggestions because I didn't play with all races, I used Dwarves Elves Orcs and Gnomes.
But actually my dream (after my trip in Mexico) is to play a "race who performs sacrifices to the gods",
trying to reproduce the cities of
Teotihuacan and
Tulum,
so I would prefer to have a few extra options in the future, for sacrifices, with "Savage races" like Nagas pr Kobolds.
Maya's god was a serpent so I would love to make it Naga
The "dig" or "not dig" limitation is the most important choice for a different game experience,
I can tell that "using actual caverns layout" for non-dwarves races is more funny that "digging your own fort underground" (that should stay a dwarves thing).
I had positive examples with Orcs, where underground lakes+caverns were used to live into,
but they still need to dig "normal-soft rock" to adapt terrain a bit. You can't obly people to build walls with wood or soft-rock.
I don't know YOUR limitations with actual DF and DFHACK,
but "you require this tool to dig harder rock" would be a good option ALSO FOR DWARVES,
dividing the game into specific "technology phases" that can't be jumped without a lot of special-structures and research.