Weak gravity and scalars

Miao Li, Wei Song, Yushu Song, and Tower Wang propose a generalization of the weak gravity conjecture to theories with scalars: gravity should still be the weakest force, they argue using various observations. For example, they believe that in d=4, the quartic "Higgs" coupling satisfies

• lambda >= (Higgsmass / Mplanck)^2

Of course, for the Standard Model, such a bound is not terribly constraining, given the huge value of Mplanck, but it is nevertheless interesting if such inequalities follow from string theory. There could exist a much more powerful generalization of all these inequalities that could play the same role for the ultimate understanding of string theory as the uncertainty principle played for quantum mechanics.