Support for Maven repository credentials was added in https://dev.clojure.org/jira/browse/TDEPS-9 but only permits a settings.xml in the default location (~/.m2/settings.xml or the one bundled with the Maven install).
Allowing user to specify the path to an alternative Maven settings would help in shared environments (e.g. CI servers where builds should be isolated). This could perhaps be done with a new optional key
:mvn/settings. I'd be happy to propose a patch if you're interested.
Alternatively supporting Thomas Spellman's suggestion in TDEPS-9 (allowing user to specify repo credentials in deps.edn) would solve the same problem and has the benefit of not requiring a separate settings file.