The most time taking event is the field change at the end of every over.

They could have made the batters change position at the end of the over like we do in gully cricket. It would mean that only 1 side of the pitch would be utilized, but I am sure it is not a huge concern. The pitches are going to be roads anyways.

The change in number of balls per innings really makes the format look dirty for existing cricket viewers. A new format should be a derivative, but should not look like a new branch all together. 10 years down the line, changes to the rules might make The Hundred a completely different animal with no resemblance to the original game of cricket.