Server-wide Database Permissions in SQL Server

We have a SQL Server 2014 installation, which is accessible by a subset of our Active Directory users via Windows Authentication.

Currently, when they log into the server for the first time they are given the sysadmin server role. I want to change this so that they belong to a more restrictive role.

I would ideally like them to be able to deal with data (SELECT, UPDATE, DELETE etc), EXEC stored procedures, and CREATE, ALTER and DROP tables, stored procedures and views.

The problem is that those permissions are database-level rather than server-level. Is it possible to have a server-level role that defines a common set of permissions for all databases on the server? If not, what's the best approach here?