Sounds good! Take your time to check things out - the timeframe of Team Avalanche's project is going to span over years anyway, if not decades
We're pretty much 3 people to be somewhat active, while the whole task would rather require 10 people with a full-time dedication: that's how understaffed we are
If you're very interested in vehicle modelling and how it would fit into scenes, I think these scenes from the desert prison will hugely benefit from your contributions:
I admit it's not really glamorous (they're not nice looking vehicles, they're rusted car bodies that are piling in a junkyard, for the most part), but I think that's where someone with your abilities would be the most helpful.
Whenever you feel like starting some work on these scenes, just post on the Avalanche forum (or PM me) and I can get you started (for one thing, I can prep the basis of the scenes with walkmesh and camera data matching the reference image, before you start anything). I can also look into other scenes featuring vehicles - maybe hook you up with SpooX (who's working on 3ds) who's been working on the environments related to the intro sequence (where you can see cars passing in front of the camera, namely). Anyway, there are many possibilities.