I think many champions could definitely benefit from abilities on a sliding scale between power and reliability. Champions with a steep learning curve, such as Azir, Kalista or Lee Sin, could definitely use at least some measure of power that could guarantee better success at lower mastery, while presenting more counterplay at the upper tiers of play. On the complete flipside of this, giving this sort of power to super-easy champions like Annie, Garen, Sona, etc. could allow them to scale up to higher tiers of competitive play without needing to overbuff them in lower divisions. This could happen with charged abilities, but also any other sort of ability that has a reliable use case that differs from an optimal use case: Sion and Warwick's ults, for example both provide damage and crowd control that can be used reliably up close, but that also have a lot of their power placed into their range, even if ulting from a distance is significantly riskier and more difficult. As important as it is to set clear success and failure cases for champions and their kits, it also helps to give them some measure of reliability at lower skill levels, even if that disappears as those champions are pushed to play more optimally and more skillfully. Conversely, every champion needs to be able to express skill, though that should also not make them completely ineffective in the hands of newcomers.