Shanks is currently playing both sides for a goal that we don’t yet know. Maybe this is all set up for Luffy but we know Luffy doesn’t want someone to influence his journey like this. Or maybe he has a more sinister goal
> Wanna make a peaceful ideal world without a single war
> To achieve it, he must destroy WG and Imu and claim all Ancient Weapons to lock it up
> isnt strong enough to have a chance against Imu
> found out about a fruit so powerful it gives the user complete freedom in power
> didnt want to risk not being able to Awaken it
> search for the chosen one child most fitting to wield the fruit
> manipulate stuff, made the child eat the god fruit, manipulatively sacrificed his arm to motivate and to boost the child's willpower/dream etc
> being a peacekeeper and gather allies until the child Awakens into golden pawn, and his annoying enemies decimated (BM-Kaidou-BB)
> use the golden pawn and his allies to war against Imu without needing to sacrifice his own life ("life is worth more than honor")
> plan to play good guy until the end after the battle, securing his win
> possibly plan to assassinate whichever survive last between Luffy or Imu, when they are in the weakest dying state
> Become World's King, assign his underlings to become kings of each nation, and rule over a world without a war
> make a harem with the prettiest girls
> finally profit