Thanks for the great question.
1) If you have digging machines, then consider installing pipes for a ground source heat pump. Once you reach a couple of meters underground, the temperature doesn't vary much, regardless of what happens on the surface. It is about 12Celsius.
2) Have a place and space for a hammock in your greenhouse. It would be a waste to leave such a lovely place solely to plants.
3) Consider hanging some LED growlights to keep things going during Winter.
4) The North side will likely lose such heat that it might be worth using multi-panel polycarbonate there.
5) You can use a water feature like a pond in front of the South side to bounce light into the greenhouse. If the water is saline, it wouldn't freeze during winter.
6) Consider a geodesic dome. Check out ziptiedomes.com and the brilliant Paul Robinson channel.
7) Space is often limited. If digging, dig deep and use trap doors to allow storage under the green house.
8) 6mm Polycarbonate twin wall is the best balance for allowing light and retaining heat, iirc. There are UV protection coatings now available. Frosted polycarbonate will disperse light and reduce "hot spots".
9) Plan for and automate ventilation and irrigation.
10) Consider a hydroponics setup.