Perhaps the most simple approach, unless you do want to have PCs destroy parts of the placeable (and that bridge example sounds impressive), is to have placeable set to static, and add invisible object placeable at the part of it. If you want to have PCs, say, climb the placeable (to the ledge you made in the terrain above for instance), you can do that via dialogue or just giving it the teleportation script (I think there were those floating around long time ago and should be still on the vault here) in OnUse section.
There are also walkable placeables, but I think I saw just few of them around, and they would need quite precise placement in the area - one I was working with allows to be placed just on few very distinct spots in the area - though that might be dependent on the tileset.