Personally, if I'm playing a new opponent and we can't agree on something as simple as terrain placement (or worse, he wants to play terrain placement shenanigans and put a hill in from of my bunker, etc..) then I just saved myself 2-3hrs of misery. I can politely excuse myself and go do something I'll actually enjoy.
We do the same method as always. Host sets up the table before guests arrive. Guests get to fiddle with anything they don't like and we dice off. The only thing I see us changing for 6th is allowing some further movement of terrain in your deployment zone to allow for logical fortification placement.