It would be nice if one could have multiple containers assigned to the same site. The use case is a multi-user site, where there users sometimes changes accounts, such as "normal user account" and "administrator".
In many case, those could be distinguished by URL, eg example.com/joe vs example.com/jill.
Extra credit: if it's not unambiguous, have the user choose in a popup or such 🙂
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This has been possible since the containers features was first introduced. You just need to use the right extension to manage your containers with URL rules: Containerise.