When I played with my friend, i thought about transport. Which can helps us to travel from one end of the map to another. For example bicycles or motorbikes and cars! You can travel with your friend, use key from the car. But it is very difficult, i think. So at first it will be very cool to travel with motorbike. GOOD LUCK TO YOU IN YOUR FUTURE.
I am from Russia and there can be some mistakes.

cars no, horses or something would be alot more in theme with the game

Horses would be cool, motor bikes would be ok too but it should require a lot of resources and fuel. Bikes sound great but they should run down your hunger fast. Maybe a wagon for transporting items?