Everything imaginable and many things not is possible. You will make kibble from goat meat, euntrepreneurs (sp?) will buy up the fort's copper supply and your fortress guard will beath him if he doesn't sell it back at a reasonable price. Goblins will charge at the gates, their trolls bashing down the drawbridge, only to be massacred by longspear-wielding dwarves riding dralthas or elephants, which will be easy to keep alive because they will munch on tower-caps and oaks as well as moss and grass.
FPS will be high, despite having cracked all three cavern layers on a fair-sized embark and having attracted the king. Modders will make everthing from spaceships to catapaults to steam-powered dwarves made of iron to iron men with jets that can be used as weapons or to fly clumsily.
Natural laws will be correct down to the quantum level. Farms will require more work than throwing seeds at soil. Adventurers will dual-wield axe and crossbow as they sail to far-off lands, plundering merchant tresure and being arrested and beaten for it.
But when you look past the details, the game will be the same as it was when Urist the Hermit and Boatmurdered were played, back in 2D. Dwarves will tantrum, causing others to get angry and the fortress to collapse. Elephants and goblns will be burnt by huge floods of magma, and elves drowned in the depot. The blood of the earth will be mixed with the sea to make obsidian, the underworld used as a trash dump, and insanely large constructions will dominate many a fort.
Why?
Because.
This.
Is.
Dwarf.
FORTRESS!