You can only have a hydrogen-helium layer with gas giant storms above a oxygenated atmosphere if vertical atmospheric mixing is effective zero. This means you have to have an atmosphere deep enough that all insolation is fully absorbed in the upper layers. It also requires that the planet have very little geological activity, large scale volcanism would otherwise induce atmospheric mixing. This has certain implications for supporting life, not least because it means that sunlight is not reaching the surface of the planet, at all. The surface being pitch black is not necessarily a barrier to life as we know it, there are Chemotrophic organisms that exist on Earth without sunlight as a direct or indirect energy source. However chemotrophy tends to be low energy and in a world with low geological activity it may not be a longterm option given the low rate of mineral turnover.
