Yeah i mostly agree with all of your ideas, so here are mine
1.Skins for forge like Snow or dessert,Rain forest, Space just different scenario's
2.Change the color of the building blocks (I know it's forerunner but it just doesnt really fit for me)
3.More precise coordinates like how they have height: 1.4 so change it to like 1.45 so you can build a lot easier.
4.Curves in the building blocks so EVERYTHING's not so angular
5.I agree with putting more vehicles in but not big one's like scarabs and stuff that would be a bit much.
6.Spawn AI's for game purposes