You make some very good arguments, Sunken.
I very much like the idea of making traps have "on/off switches", and of building trap-lined corridors that dwarfs simply know to avoid.
I already use that idea, myself, as a "roleplaying" thing.
My Fortresses tend to be guarded by very extensive labyrinths, with multiple tunnels and entrances/exits to any single destination.
Maybe some traps could be "pedestrian-friendly", with only a 1 in 1000 chance of accidentally setting them off (provided you know they're there, and how not to spring them), while others could be set off by anyone walking down that particular, rather dusty hall.
I'd also like to mention net traps. Nets may not seem too dangerous, they're just woven cloth, right? Gentle, peaceful cloth drifting down over you like sweet cherry blossoms.
Sure they are!
Until you start weighting them down with lead, weaving (poisoned) fishhooks and razor-blades into them, glueing crushed glass to the cords, filling them with vipers and scorpions, or even soaking them in lamp-oil or strong alchohol, and setting them on fire.
Net traps, especially ones woven from spider silk (nearly impossible to break), can be as innocuous as the cage traps we already have, or as lethal as a guillotine, and as tortuous as an iron maiden. They also have the advantage of size adjustment. A net trap can be set for one person only, or used to cover an entire corridor. All that's different are the size of the net (obviously) and the degree of power used to move it, and it's unfortunate occupants.
Nets would also be suitable for both outside and inside use, could be hidden fairly easily, and manufactured by even very low-tech civilizations.