Yup, that is exactly what people found on beta, they found that you needed to gain 2k drinks from incidents in total in order to make both buildings level 6, if you only get the one kit from league.
So with that, its either get lucky in always doing hard tourney tickets so you get silver, get lucky with incidents, or spend diamonds to finish off both level 6 buildings.
Its essentially a level 12 building, the highest the main building's been from an event.
If your close on drinks, that means incidents have been kind to ya
Glad to see that someone confirms my experience. 2k means 100 drinks a day from incidents! That's incredible luck. I've had some lucky incidents but not nearly enough.