I've been playing build 41 for a while, and one thing I really like is the protection system. The trade off of getting too hot, or maybe moving a little slower for some protection is something I find very interesting.
It would be cool to be able to use the metalworking skill or even the tailoring skill to make homemade armor. Making a beefy metal suit would be cool to feel like a tank, but the trade off might be you can't attack or move nearly as fast. Or you could make a leather armor that is a more middle ground.
Also, when it comes to vehicles, it would be great to use metalworking to make a impenetrable zombie crushing machine, with the trade off of slower speed and less fuel efficiency.
On a side note, it would be a great addition to be able to fill bathtubs with water. This is something I do when there is a storm and I think the power is going to fail. It would be a good common sense thing to do in your starting house, or where you decide to make a base in the early game to help boost your chances of survival.