If you're getting into time travel, you can't overlook Changeling: The Dreaming. It has this wild take on time where fae can manipulate time through dreams, which can lead to some trippy storytelling. The mechanics not only let you shift timelines but also explore the emotional weight of past decisions.
Another system to consider is Timewatch. It's built around time travel from the ground up and lets players jump between timelines to fix issues or even create paradoxes. The action and consequences feel really impactful because every decision can ripple through time, impacting future encounters.
Are you thinking about running a campaign focused solely on time travel, or will it be a subplot? I'd love to hear more about your ideas!