I don't think Amazon would mind being in that position.

Realistically though, with 3 major cloud vendors to choose from, I don't think the danger of app-store style control holds in the same way.

The App Store is fundamentally a problem because there exists only one (eg apple) or one is inherently privileged (eg android); on a PC/servers/cloud, this isn’t likely to ever occur.

Although, I suppose steam is an argument to the alternative, though they haven’t successfully abused their position afaik (like their attempt to monetize general modding communities across non-valve games)

Even if it does, I don't see how they can lock them in just their version of "app store". If it takes off, I can see GCP, Azure and others offering similar deals too.