Builder teamwork
A future update with this feature would be cool. If you start to upgrade or build something, all the free builders should work on the same construction to save and shorten time. So if you have two builders working on the same construction the time to be built would be halved, and if you have 3 builders working on the same one, time decreased to a third and so on. And if you put another building to be upgraded at the same time, the game will consider the time that will take and divide the builders in a way that the constructions will take the shortest possible time to upgrade. It would be really great if supercell considers this feature because it will save a lot of time.
