Your idea sounds too broad for me. You'd need to elaborate on these aspects:
1. What exactly these gangs are. Sounds like mafia but they could be hired guns.
2. How exactly traveler and player travel between universes. This will have impact on the game or not depending on game design.
3. What will happen if player fail to save a universe. This will define game's linearity or not.
Wait, #3 reminds me to something.
4. How exactly this traveler destroys a universe. This will also define what player could do to prevent it.