This development, and the possibility of migrant waves having less than community-spirited individuals, makes me think that I want to consider a sequential entrenching policy[1] for my various migrant waves, because right now I'm feeling paranoid about getting unexplained deaths. I'm sure, once I experience it, I'll take it all with the same pinch of salt as I do with FB-appearance[2], but right now it's making my heart flutter with not a little trepidation...
I can't see myself accusing nobles, like I don't currently 'accidentally' designate nobles' bedrooms as magma-storage-tanks, but that doesn't mean I can't see the advantages. (As well as the disadvantage, but YMMV, of the actual culprit being free to stalk the back-streets of this dwarven Whitechapel, unmolested. (Which is more than can be said of the regular inhabitants of that dwarven Whitechapel, obviously.))
[1] Initial wave digs out a starter fort/living area, and buds and starts to fit out a further area. When another migrant wave arrives, send everyone into this new area and leave the old one for the migrants. Prior to the next migrant wave, get one or other of the existing colonies to dig out a new area so that they can move in so that their predecessors can move into their up-til-now current area, and shuffle along like that until the migrants are accommodated. Extra challenges (airlock/dump-in-hole-and-reclaim) for any necessary material and goods transfer between isolated colonies, of course. I also foresee my organising each living unit as being a bit like a subterranean courtyard (perhaps multi-Z, with balcony) with living quarters at one end, workshops at the other and all other needs satisfied in the middle, and with a panopticon-like compactness, insofar as lines of sight. Hmmm, but what about the various military units? Well, perhaps I could... <mumbles to self, you don't need more waffle about this, I'm, sure>.
[2] So, at least Toady is upping the ante, because all us veterans got a handle on land-defences to stop invaders, etc, and now they might come on flying mounts. The occasional underground area became something to be easily dealt with, and then the current caverns came along. Titans and other monsters might well have been considered blasé, and then along come Syndrome-giving FBs, etc..