I think that I disagree with your opinion that developers should provide Create Table or Index scripts. Developers shouldn't have to worry about how a table gets created, that's a DBA's job - especially if they're the "gatekeeper" as you indicate. Those questions you raise - about Identity Columns, indexes, constraints, etc. - developers won't think about nor rarely know the answers to, and I'm not sure a DBA should expect them to. Once those questions are answered - which can be done in concert with the developer - the DBA should be responsible for creating the scripts to get the job done. That way it's done correctly - and nobody gets hurt! 😉

My 2 cents.