While I assume the base mechanics will get reworked, they haven't said much or even if there will be any added features unless I'm mistaken.
I wouldn't mind the environment having a slight impact on maybe stats or something. Wet/cold/too hot.
Or perhaps much shorter stamina bar or it drains much faster at high altitudes. It'd go a long way towards giving you the impression that the terrain matters and has an effect on your character. Especially when you're up on what should be really rough terrain like mountain tops.