When creating a Pull Request, the field "Reviewer" could be automatic filled with a random reviewer (probably from a list of pre-defined reviewers for that project).

This way there is no need to "choose" a reviewer.

 

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Latest update from Atlassian 2024-04-22

Randomly assigning reviewers is possible using the recently released code owners feature in Bitbucket Cloud: https://bitbucket.org/blog/code-owners