Okay - let's work this way.
Betts has to be in the Top 4 - because he is one of their 4 best hitters, and none of the other hitters make reasonable sustainable cases for inclusion over Betts (Travis Shaw, Holt, Vasquez, Bradley, Ramirez). Could you argue he should be in a position with more RBI potential? Maybe. Given his speed relative to the others, leadoff makes more sense. Aside from Ortiz there is not a terrific amount of on-base differentiation.