Shh, such petty plans.
Sigh, I just spent a day building 300 hatch covers and 1000 mechanisms just for the first 'welcome' trap of my dungeon. Unfortunately the enourmous wealth created by my godlike chefs attracted a dragon just before it was completed. And the dragon, dont you know, rushed in to set fire to my on-going trade at the depot, thank you very much. I don't have to describe the ridiculous consequences that befell my emotionally unstable dwarves after that.
That's where plans come from. VENGEFULLNESS. It inspired my current plan of creating a large upward spiraling tower, just 3 tiles wide to allow the caravans to enter. I am looking forward to watching them roll their wagons 15 Z-levels up into the air, and down again). It will of course take ages to build, but at least I get to ponder a million ways to create the perfect kill-chamber 1000 feet up in the air.
My favorite so far: At the top of said spiraling tower I will create a corridor. It will consist of two 5x3 drawbridges and a single 1x3 wall section between them, upon which are 3 pressure plates. Step on the plates and the bridges retract, and if my calculations are correct, they will land exactly outside of the tower entrance. If anyone survives, feel free to try again!
For an added bonus, I'll make the landing site a large 10x10 drawbridge with a pit beneath, so that I can open it every once in a while to claim the growing pile of loot and bones.
Yes, I can see it now. My fortress, it will be like a big monster, eating the miniscule goblins and tiny dragons. Ah, we'll see who's mad yet!
...now let me get back to my 5-hour and counting search for the perfect site (I thought I had it, finally, half an hour ago, until I realized the 'white sand' the embarkment screen had advertised was non-existant.................)
EDIT: Oh, I found a site, and there's a sweet magma-pipe here! I wonder how hard it will be to mold the entire entrance from pure obsidian... ^^