If they are going to leave the outlines unchanged, it confirms my suspicions that this arrangement is about cutting out the individual speaker's input into the final presentation of the talk. The speaker is going to be forced to cut out his own personal anecdotes, stories and analogies to get in all of the information on the outline. They're tightening the reigns, folks.
Forty five minutes allowed for a significant amount of personal freedom for each speaker to structure the talk in their own unique way. Thirty minutes per talk is going to ensure that the talk that Speaker A and Speaker B give using the same outline will sound almost identical.
This new arrangement is in line with the instructions Watchtower conductors received a while back telling them to cut out their own use of additional study materials that were not included in the article. They were told to stick to the information as presented in the Watchtower magazine only. This 30 minute talk thing is just another step in that direction.