I’m gonna say no on this. Alliances are meant to be temporary. The clans still serve a purpose as being persistent. With temporary alliances, they can be cancelled at any time. Managing with your clan would be far more difficult if you had to manage a friends list, especially since your mood over who has access to certain items may change on the fly in that scenario. Last thing you want is someone who suddenly decides to downgrade your relationship status when you’re not paying attention or logged out. At least with clans, you MAY be kicked out, but it’s far less likely that someone will modify the clan status since it’s MEANT to be a persistent feature. You only allow people to join your clan if you trust them. Your alliances are meant to be just that, temporary alliances.
Now if they have alliance accessible chests, doors, etc., THAT would be a nice feature. It will help you to keep your own stuff separate from loot shareable storages and rooms. Perhaps just a toggle feature to change doors and storage to alliance accessible. This could be similar to the toggle for disable/enable auto close. You could even apply this to work benches.