I just breached hell in my last game to end my fort. ~25 8-11 Skill level Dwarves waited for the demons. They took out ~70 of 100, only cladded in mediocre quality steel. Think with Welded Mithril, more training or crossbowsquads i could have handled it.
An idead that crossed my mind after you talked about adding time to reactions - would it be possible to "breed", as in, trade/spawn/embark with an animal, butcher grown up version, loot item, item allows to get different animal, and so on.