It isn't really confirmed, but many people have speculated that WBC is just a scam, they do whatever possible to provoke people into doing something they can sue over. They don't really believe what the signs say, they only exist to spark controversy and make people react and do things worth suing. More info here.
So have fun with it, but just don't do anything they could sue you over.
I love the premise, but I think the engine kind of hinders the game from reaching its full potential. Those awkward curved jagged edges when you look down paired with the screen roll give me motion sickness, but I know that's just how the voxel engine works. Also a longer view distance might be nice. I think the engine's website mentioned the fog can be tweaked to any distance, so maybe it was put that way for the sake of balance.
I don't play all that much, since I'm on Mac and never really feel like booting into windows to spend half an hour trying to find a working server.
Firing Range, Nuketown, and Shipment seem to be the high ones so far, and also they'd be (somewhat) affordable to reproduce, compared to most other maps at least. Call of Duty is also immensly popular, so that would bring in good (theoretical) income. However I would love to pay some homage to the CS fans as well, de_dust2 is possibly the most iconic FPS map of all time but I think making it would be rather expensive.
I have all the suggestions put into a spreadsheet and I'll keep adding them in for a week or so, keep going people!