Let's have an FB that breathes dust that turns things into dwarves! World domination! At least until the global tantrum spiral.
Inverting this: What if there came a FB that turns things into elves... Armok protect us. Though I'm pretty sure that's why we build levers to flood the entire fortress with magma.
Also, I'm wondering if we can keep control of dwarves after genetic reconfiguring. Though I guess caging then releasing them during a siege always works.
A little fantasizing if genetic mutation does lead to the dwarf going 'stark raving mad':
"Sir, it took us four grown men to capture that... thing. I don't like keeping it around."
"It is not your place to question, Recruit. That creature was once my brother. I will not have him killed, even if he has ten legs, twelve arms, three heads, breathes acid and fire and looks like a corpse that has been out in summer for a week."
"Y-Yes, sir."
-A demon breaks through and enters the courtyard-
"SIEGE, WE HAVE A SIEGE!" -Urist McCaptain charges to spar with the demon, but is forced back. The rest of the militia is dead or dying, except for the Recruit-
"Recruit! Pull the lever."
-The Recruit hesitates-
"Recruit! Pull the damn lever! If we have to die, let's at least make sure these bastards all die with us."
-The Recruit flips the lever and a shriek echoes through the fort.-
"WHO TOUCHED MY ALE?!?!"
-The Captain, slowly succumbing to the wounds he receiveived let's out a small chuckle- "Good to see he still has his priorities."
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Also, let's make elves lethally allergic to wood. Because love hurts.