creating a branch for the release is no option?
It might be, but that's for the release manager to decide, and he has chosen the alternative option of freezing the repository.
that's odd, because I do that all the time. i.e.
1 - create trunk snapshot by branching 2 - build release kit from branch 3 - tweak snapshot in branch if necessary, repeat from 2 4 - when the kit is solid, tag the final branch 5 - merge relevant changes back to trunk
It's more complicated than the current procedure.