...for the record, I don't take anything online seriously so I'm just having fun.
As far as block differences with traps and what not, a model is a model is a model, the xml controls what it does. You may have to set up a model differently in unity to allow it electrical hookup, or to walk (entity), or to be held (items), but that's all trivial. XML handles the rest.
...lying a little bit, entities are not yet natively importable by 7days, but only because the bone names don't match theirs, so it could be done.