Nice idea, but probably to much restrictive.
A much more useful feature would be to have some kind of meta model (your ansi model?) without db specific features, but that is linked to several database specific models. So the idea is to maintain tables, views, columns… in the meta model and all changes reflect to the connected models (some kind of inheritance). In the database specific models you can adjust the database specific properties.
That is exactly what you need to maintain one single PDM that needs to be ported to several database systems.
Perhaps this is easier to implement than one might think: Just add the connection relation from the database model to the meta model and remember the version. Only changes made in the meta model are propagated. After activating the specific model check for a version update in the meta model. Then just apply the changes made in the meta model (use simple model conversion algorithm on the change set)…
Looking forward to see this in the next beta ;-)))
Just my wish for christmas /\