I had an idea for a book with time travel a while ago. I went with the multiverse.
The main character was obsessed with the future, but his time travel machine could only ever go back to the past and back to his current time. So he set out to travel to the past in a parallel universe. He went back to the roman times and helped them and brought with him books, technology, weapons, etc. Basically ensured the survival and evolution of the roman empire. He would stay there for a year at a time and travel back to his time to gather more books and other technology. Making sure to bring only what the romans were capable of learning at the time. He would show up at 50 year intervals in the roman universe. This quickly made him seem like a god to the people there. The roman empire spanned across the entire globe rapidly and they were making leaps and bounds towards the future. The goal of the main character was to reach past his current timeline's technology level and reveal himself to the romans as "just a man" once they were technologically advanced enough to understand that there is no such thing as a God.
There were obviously some story arcs weaved into this to make it more interesting and not so certain.
So yea, I'd say the multiverse theory can make things more interesting.