Grek, I think the flaw with that design is if yr little dwarf doesn't run faster than water. If the water beats him to the door, then he'll just flood the airlock too when he opens the door to flee. Even in the current system with anti-flood generators you only need to build the floodgate a space away from the digging location, wire it to the lever, keep it open while the dwarf breeches the damn/digs the channel, and when (read: "if") he gets washed back into the farmroom, shut the flood gate and allow the antiflood to save him (though in the new version, it just takes making sure not enough water gets through to still drown him once the gate is closed).
I used to place doors every now and then when I was sinking for the river, but I quickly learned that a door is only good to protect the rest of the fort and not good if you don't lock it and the dwarf makes the dreadful mistake of saving their life by opening or closing the door at the wrong time.
Toady, regarding falling objects, do ramps act as the upper surface? If so, will an object falling on a ramp be pushed (deflected) off it somehow, or will it come to rest on the ramp?
Just wondering if in the future we can create some sort of cascade effect with non-liquids, without using liquids to flush them off surfaces.