Structures in SC2 are key to the game, if you don't place the right buildings at the right times you are not going to have what you need to win. Having events for different key buildings like unit production buildings, tech buildings and new bases would really benefit players. They can track scouting patterns and take a look at their placement, reaction time among other things.

for example
Protoss (Nexus, Gateways, Cyber core, Twilight Council)
Zerg (Hatchery, Spawning pool, Roach warren, Lair , Hydralisk Den)
Terran (Command Center, Engineering bay, Barracks, Factory, Armory)