Not all new tech is as good as it sounds - what I would do and why:
1. Hot water - forget the instant gas fired tankless - why? You have no hot water if power is out. Also, they are poor if you need a volume of water. A high efficiency tank is great. Add to that a hot water circulating loop - you can't do this with a tankless system. Adding the loop with a tank system gives you hot water in one second instead of waiting for all the cooled water between tank and faucet to be expelled. Add a timer-circulating pump, and you are not circulating hot water at night when you don't need it. All old tech that works better then new tech. If you want to go tankless, then spend the money to put one near each cluster of bathrooms, or you will waste water waiting on hot water.
2. Natural gas heat - if you live in a colder climate. Heat pumps just pump out luke warm air. But if you can go dual fuel, and use a heat pump sometimes and natural gas others, you have best of both world.As others mentioned, radiant heat is a great choice, but you then have to install forced air for AC.
3. Some kind of air-exchanger that uses the exhaust air to pre-condition the incoming air - i have not found anything for residential I like in this area. But, if you have a tight house, and you have various exhaust fans or central vacuum, then you should have a way to supply fresh air.
4. Bath fans - I like fantech brand - the motors are remote mounted, and they are super quiet
5. Central Vac - I can't live without it, but I have a pile of dogs and cats and no carpet. Check out something "newer" called "Hide-a-hose" - i have not tried it yet, but plan to in next house. No more hose to store and get out. It stores in the pipes in the wall.
6. Shower Pan and walls - check out Kerdi - I will never do a bathroom without it again.
7. Quad electric receptacles at the night stands in bedrooms and kitchen counters.
8. Cat X (whatever is the Ethernet standard at the time)
9. Network rack and patch panel - I have it in the basement - all home runs of Cat 5e and coax to this location.
10. AC outlet in closet/pantry - you want your wireless router in the center of the house - why not in a closet. Also, you never know where you may want to plug in a flashlight or something.