You'd need lots of brass.
I think tech trees would be a terrible idea for an in-game set of events. Even if it were possible, it would probably follow suit with the rest of the game, where the dwarves would just invent whatever random technologies they were interested in.
However, having different innovations occur during worldgen would add some interesting flavor (imagine being able to date ruins based upon what techs the civ used in its construction). Also, if Toady ever finds a way to add things like generated rocks, monsters, or civs to the worldgen without it looking like so much "static" (his term), it seems feasible that certain random technologies could exist, perhaps even following a natural progression. Scenario:
Random goblin civ is populated in tundra/glacier terrain
Goblins are exposed to certain resources given their environment: ice, fish, etc
Goblins "invent" bone-related industries (crafts, crossbows, bolts, daggers?)
Goblins "invent" ice-related industries (crafts [ice sculpting? heck yes], weapons [icicle ballista bolts, ice arrowheads, ice swords])
...and then you are attacked by a race of goblins with masterwork ice maces that menace with spikes of fish bone. T'would be awesome, especially when they run past your magma moat and all of their weapons melt.