Look at the openers from Australia(Warner & Finch), India(Rohit & Dhawan) and South Africa(Amla & de Kock) all of them sides will be going from ball one from both ends.
Amla is not exactly a big hitter from ball 1. He rotates strike and plays a long and deep inning. It is Quentin De Kock who hits from ball 1. I think this is the thought behind a Bell and Ali combination: one will rotate strike and play a deep and long inning while other will hit big. Hales takes his warm-up time before he starts hitting big.
Finch also rotates strike before going big, it is Warner who starts hitting (mentally and spiritually) before the first ball is even delivered!
Also, the oppositions will be prepared for all these big time openers. They will bowl to cramp them up. Let's face it: we may not see a lot of fireworks by these openers as they are known entities to the opposition bowlers. If I were a coach for one of these non-tri-series playing teams, I would be taking a lot of notes.