Doesn't the IDE force you to update your data generation plan if your schema changes anyway?
From the MSDN:
When you create a data generation plan
in a database project, the plan is
based on the database schema of the
project. If you create a data
generation plan and then the schema of
the database project changes, you are
prompted to update the plan. This
behavior occurs in the following
cases:
- You create a data generation plan in a database project that does not
have a schema yet. You then import a
schema into the database project.
- You create a data generation plan in a database project that has a
schema, and then the schema changes.
In both cases, you are prompted to
update the data generation plan when
you open it or when it becomes the
active document. If you do not update
the data generation plan based on the
schema changes, you cannot continue to
edit the plan. You can close and
reopen the data generation plan to
display the prompt again.
More evidence from a blog on this subject:
... the schema of the objects inside the database has to match the table inside the database project.
I guess you could dig into the *.dgen file and do a pre-build step (or something similar) that would ensure it always matches your DB schema. Maybe that would automate things enough.