Server-wide Database Permissions in SQL Server
So basically it sounds like you want to give this group of individuals db_owner access to all databases on the server.  The way to do this is:


Create a local group account on the Windows Server (e.g. \\MYSERVER\SpecialGroup)
Add the AD accounts to that group.
Create a SQL Server login for \\MYSERVER\SpecialGroup
Then create a job, that runs every night (or however frequently you want) that loops through all your user databases and issues a CREATE USER statement for \\MySERVER\SpecialGroup and assigns them to db_owner.