Minato was stronger than Tobirama so idk what you’re cooking here lol
Minato is probably a little weaker, but my point is the fact that they use the same Jutsu doesn't mean much.
Shanks can't be like Roger when he doesn't share the same dream, doesn't have the will of D, doesn't mind insults(which makes him more like Rayleigh), doesn't have his rivals bend the knee to him,doesn't have an era and isn't hated as much. If Makino's kid is Shanks's he won't grow up hearing people say he shouldn't have been born and be hunted down.