Watch this old E3 video of the original Halo Wars. The game didnt look much like this come launch but I think the building designs looked great.
I think it would be great if you could see mechanics building the warthog for you. Would be a nice touch. Hornets being built in the air pad hanger, Infantry training up firing at targets etc. Would be a nice visual cue on how far through the build the unit is, once the turrets lowered by the crane onto your scorpion you know its almost done and the enemy could scout this too. Not sure what would happen if your base was under attack though, would they just continue? Haha
The buildings in this clip look great, fit for their purpose.
Wonder how the banished would look with more detail.