Upgrading metadata schemas from 3.0.x to 3.2.x is a bit problematic, at least in my recent experience.
I understand that should be differences due to new features in 3.2.x, but actually the only way to fix the issues is a try/error mechanism, not very optimal.
I think apart of the schemas documentation (that lacks of description for many of the xsl files used in the layout folder and are mandatory) we should manage the changes in a specific manual page or wiki page in the project.
So if a change is done in the schemas requiring new xslt templates added/name changes/etc, can be clear what changes should be applied. Apart of this page, for sure requires that when any of us do such changes, the proper documentation is added.
Would be good to hear from other developers what is their feeling about this.
Related to the schemas documentation, I'll check to improve the documentation about the layout folder xsl files.