I know we've talked about this a number of times with a number of people but I wish to reopen Adam Machanic's 243986 suggestion on the need for INSTEAD OF triggers for DDL operations. DMF now makes the need for these even more pressing. Many operations are way too expensive to roll back and some operations such as CREATE DATABASE are unable to be rolled back.
It should be possible to issue DMF policies for say "you may not rebuild indexes during 9am to 5pm Mon to Fri".
INSTEAD OF triggers would also allow updating the DDL before executing it. For example, it could be formatted according to an organisation's standard before being executed (and stored). You could also automatically insert comments on who performed the operation into the DDL for CREATE or ALTER. You could potentially even insert a checksum or procedure lineage information automatically.