Realistic environmental model won't work in civ/VP since we have a victory condition limit, so you can practically say "screw the world I'm going to the moon" and just win/end the game without caring about the aftermatch.
I agree with this. Even if the proposal had everything set and specific, there's the issue that the environmental part would likely be only as relevant as the Giant Death Robot. The whole environment debate only really started after the Cold War (Atomic Era), so the proposal would only realistically apply to the Information Era. Yes you can argue that human activity was already shaping Earth at least since the Industrial Revolution, but it is a far fetch to say that environmental concerns played a major role during the world wars and the Cold War (Modern and Atomic eras).
Being so late, the effects would have to be really drastic to matter, and potentially such a major disruption to gameplay that it feels completely disconnected from the rest of the game. With the scope we have now, it only seems to fit as a WC proposal.
Reforestation can be interesting, but potentially too powerful for specific civs (Brazil, Maya, maybe Siam and Iroquois as well) if it unlocks too early.