I am confused.  Let me clearify what you are trying to tell us.  OK, you made a copy of production database and put it on test servers.

1.  You remove users login from Sysadmin rights (good) and make them db_owners of the database that you just copy.

I think it is alright to give your developer database owners on their database that they are developing on.  They can still create new table, views and stored precedure as long as they start by specifying that they wanted dbo to own it.  For example:  crate table dbo.test (data varchar(10)

by specifying dbo.objectname, this object will be created under dbo and owned by dbo.

In any circumstances, I never let my developer be sa on any of my servers.

mom