At the moment buildings are vulnerable when being built, as well as a bit vague as to whether they are unbuilt or damaged. What I suggested on the IRC channel was that they should start, like walls semi buried, and have to rise out of the ground as they are being built, like walls. If they are attacked while rising , they don't sink, just take damage, and carry on rising.
Could end up flipping vehicles parked too close, or closing off a passage that you thought would be open. If there is going to be any kind of animation, it should be a proper 'unpacking' one, but we know that won't be happening for a long time.
You can already get to crazy places with engineer buildings(or at least you could previously), imagine standing on top of NF barracks while it builds? You'd be able to jump onto mountains.
something that would be much cooler than building rising, is having it build up in sections, adding a layer ontop everytime edit: I made a quick example of what it would look like (if you cant see it, the gif is 500kb :p)
IIRC, Krenzo said he once had a system like this (well, the building was wireframe and was then filled in), but the FPS hit was gigantic.
devide the building in different parts and then slowly make the building transfer from opague to solid per section?
Hows abouts when you drop the building, you get something that looks like a foundation for the building instead of the building itself. Perhaps have it go through several logical states of build-ed-ness that rise up from the previous state of build-ed-ness. Or something. That got reduced to confusion rather quick. Ignore me. EDIT: Oh, yeah, obviously the foundation model and the various "being built" models would disappear on completion of the ye aulde buiding.