I'm almost ready for a release, breaking for late breakfast so I thought I'd give y'all an update.
There will be, in all, eight types of golem: Iron, Obsidian, and six "lesser" stone golems (one for each magma-safe stone other than obsidian than can form entire layers)
Iron golems will remain mostly as described, living on average about 1600 years, gaining combat skills quickly, and having others frozen in place. Only iron golems will be able to enter martial trances. It will require 3 small gems (if I did it right, if not I'll change it to 1 large) and 128 iron bars to create an iron golem.
Obsidian golems will live, on average, about 800 years. They will not learn as quickly as iron golems, but are otherwise much the same, other than being notably more fragile. It will require 3 small gems (if I did it right, if not I'll change it to 1 large) and 128 obsidian blocks to create an obsidian golem.
Lesser stone golems will live between 160 and 320 years. They will learn combat skills slower still than obsidian golems (about the rate of normal dorfs). In addition to being unable to gain any ranged combat skills, their noncombat skills will rust away very quickly. They will, however, gain wrestling much faster than obsidian golems. They have only one eye, and are much larger than other golems (slightly larger than a human) require them to use larger equipment should you decide to attempt to arm and armor them. It will require one small gem (if I did it right) and thirty-two raw stone to create a lesser golem.
Golems are universally marked as non-living now, and so will not be able to be reanimated if they are deanimated.
Notes:
It is likely different kinds of stone will stand up better or worse to punishment, but all should be fairly tough. So far in my testing, obsidian golems do fantastically in 1:2 (golem to goblin) ratio settings without weapons or armor or skills. Blunt weapons will be the most likely to cause significant damage, followed by axes- spears are pretty much useless. Bolts mostly bounce off, or chip off pieces of stone (which does nothing but piss the golem off).
Golems who lose all limbs should be euthanized, as I didn't give them mouths so they can't bite.