I'd really like to see more realistic ground (contact) physics with different textures and terrains. Someone might walk differently in a desert environments vs a forest environment vs a snow environment for example. If there's debris on the ground such as small rocks or other debris it may cause the character to adjust foot contact to compensate. Sloping features could also be incorporated and modeled. Walking is a big thing but vehicle movement in these environments is also something that can be drastically improved upon.