I like the idea of removing the complete trap immunity and replacing it with luck-based approaches.
And I also think there are ways to prevent players from just building massive trap corridors, for example I think it is not overkill to be able to place 10 weapons in one weapontrap - with only 1 or maybe up to 3 weapons you need much more space. Then cages should have a size imo so that creatures to large for the catch are not easily catched - maybe you should be able to order small, - , large cages to be made - but there shouldn't be something like a size 20 cage. (We can create other means of catching a dragon for breading, I don't want to take that away
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Then a mayor change would be to make traps in a way so that your dwarfs are not able to evade your own traps - to compensate for this you could have levers to enable/disable traps. This makes traps much more dangerous for your own military as well, so think about building them twice before you have a weapontrap corridor infront of your barracks.
Finely traps could need regular checks/small repairs so if you place hundreds of traps you need a small mechanic squad running around all the time to keep them working.
In combination with [trAP_AVOID:50] or something like that traps are no solution to entire entities but only a nice help in combat if placed well.