Solid overview. Two things that bite once this is in production:

Shared singletons hide version skew. If the host is on React 18 and a remote ships expecting 19, singleton: true hands the remote the host's React and requiredVersion only logs a console warning, it doesn't fail the load. You find out at runtime when a hook behaves differently.

The Suspense boundary isn't enough on its own either. If the remote is down or remoteEntry.js 404s, the lazy import rejects and Suspense won't catch that. You want an error boundary around RemoteCart with a fallback so one remote going down doesn't blank the whole shell.