As I was reading the Silmarillion I kept thinking of it in terms of the World Generation now being worked on for DF. I have to imagine that these two suggestions have been made before, but I couldn't find them in the search so forgive me. Both relate to Fey moods (which occurred relatively often in the Silmarillion (and yes, I know Universe_of_DF != Universe_of_Tolkien)).
1.) Military dwarves/creatures should go fey. They should get a temporary insane bonus to agility and strength and whatnot and be able to accomplish incredible feats, like the single handed slaying of a dragon or laying waste to an overwhelming goblin invasion. Naturally this should not happen often. If the dwarf survives, he/she should then become a legendary warrior of his/her weapon of choice. Perhaps this is in and I've never seen it, but I've played a lot of DF.
2.) Fey moods should happen as historic events. Combat fey moods should allow even a weak civilization to conquer huge chunks of territory. Object creation fey moods should create incredibly valuable artifacts (e.g. the Ring of Power, or the Silmarils) which should add bonuses to the holding civilization (faster reproduction, more resources, etc..., or to the entity holding them like unnaturally long life, hit point bonuses, etc...) but also be a cause for jealousy and dissention. They should be capturable or giftable and even tradable, but should be few in number and eventually end up (in year 1051 or whatever) at a particular place and be accessible to the adventurer or to capture via armies in fortress mode.
I have no doubt that Toady has thought of these things, and little doubt that others have posted about them, but I was so excited that I just had to.
Cheers! May your losses be incredibly fun!