Make Source Repositories configurable separately from a build

My company currently has 34 plans configured in Bamboo.

Of these 34 plans, there are only two source repositories. One Subversion, and one CVS (we are slowly migrating to Subversion).

It would be nice if we could configure those two source repositories (including authentication credentials) once, and then in each plan we would specify a repository and a URL within that repository. An optional per-plan override for auth credentials would be a nice addition.

This would be particularly nice for us, since our IT guys insist that we change passwords every three months. We have to go through all 34 plans and change the password, one by one!