Sending from one mint to another will need to be settled in LN. So you better look carefully what kind of of a back end LN node your uncle Jim is running. Truth is that most uncle Jim's won't have this kind of a setup, so then it turns out to be another more centralizing hub and spoke model.

There's a lot of hope in fedimint. I'm not seeing it yet. And honestly I hope they aren't building on sand.