This has sort of been talked about in the suggestions, but I´ll still tempt the fate posting this question here:
What I am really interested in the OFP2 engine is, will it be possible to model underground structures, like caves and tunnels that are completely below ground, possibly with above ground objects eg. houses on top of them? How about trenches and foxholes?
In effect for this to work the Z coordinate in the ground would need to be given negative values, which might be a bit complicated, dunno.
Also, how about water, will the people (and animals) be able to swim?