Does SFDX add any way of automating the setup of business hours?
You can push/pull/deploy/retrieve BusinessHoursSettings as part of your source code repository. You'll find this file in /settings/BusinessHoursSettings.settings-meta.xml. If you're just getting started, you can retrieve it from an org (along with other settings) like this:
sfdx force:source:retrieve -u usernameoralias -m Settings