Half finish Gem boosts

I think the possibility of instantly finishing something such as a building is a good touch to the game, however many situations when you get to the higher level upgrades, the build/upgrade/training time takes a long time, which costs lots of gems. I think it would be a good touch to the game if you were to add a second option to cut the build time in half, this would be a cheaper way to speed up the long upgrades that could cause a decline in your performance in the game, such as if you were upgrading a defence, it would not be usable for all of the attacks that it is being upgraded in, the longer the time, the more attacks. Please consider this idea. Thankyou.