I've invented a device that everyone needs to implement!
I got bored with one of my current fortresses. I've seen people talk about how they put people in their danger rooms to kill them (migrants/elves) or level them. Since my industries were working fine, I figured I'd mess with the migrants. I made a danger room between the entrance and the main fort (I had my depot there, but deconstructed it and built it deeper). This forced anyone who was entering my fortress to pass through my danger room. I had double doors on both sides, and once the migrants filtered in, I locked the doors. A few got stuck outside, so they'd have to learn to wait their turn.
I locked them in for a few days and out of the original dozen or so migrants I locked into the room, I had a survivor. I couldn't believe it. A migrant didn't throw himself upon my spear traps. Being a sick person (most of you know where I'm coming from), I began piling all my non-military, non-legendary dwarves into this danger room, now dubbed "The Darwinator". And awaaaaaay they went! Most of my dwarves did, in fact, die, but the ones that came out were better. Changed. I mean, they've seen stuff, man. Surprisingly, there hasn't been a tantrum spiral. You'd think a mother of three would bitch and moan after seeing her husband and children impaled. But she was ecstatic when she was allowed to hunt elephants again.
I've also decided to keep the depot inside the fortress during spring. For obvious reasons.
Here's a quick breakdown from my perspective:
PROS:
Gets rid of any population issue
Removes useless dwarves
Trains the ones that deserve to live
Allows the creation of a master race
Because f- the elves
CONS:
DWARF FORTRESS