SharePoint Online (2013) - Security Roles for Technical support resources

Here's an article that explains all the admin roles available in Office 365.  But in general there really isn't a way to give someone admin access to SharePoint without giving them access to the underlying content (or at least the ability to take control of the underlying content).

https://support.office.com/en-us/article/About-Office-365-admin-roles-da585eea-f576-4f55-a1e0-87090b6aaa9d

This isn't quite the same, but there is now Audit tracking of administrative actions in SharePoint Online through the Security and Compliance Center.  So if you give the support personnel the SharePoint admin role but set policy boundaries on what they can do you will be able to check the audit log to identify any time they overstep their authority in the policy.