1) whole house generator
not sure if the area you are building on has frequent power outages AND if the outages are long OR need to ensure sump pumps are always powered, etc
In my current home in NJ, my block was out for 2 full weeks after hurricane sandy. this was the first improvement after we purchased.
2a) stated already but add CAT6A or CAT 7 ethernet wires (at least 2, 1 as a backup)into every room while the walls are open. allows for direct connections for the home office, apple tvs and to add more access points for wifi, if needed.
you might even want to drop some lines in the ceiling so you can ceiling mount access points.
2b)think about exterior grade CAT wires if you want to have outdoor wifi access points and to connect cameras
3) blocking for hanging stuff - this needs to be discussed with the builder before insulation/drywall. this should eliminate the need for moly bolts for towel racks, toilet paper holders, wall mounted tvs, cabinets.