I've done the same technique a few times. I used Sybase for one, and MS SQL for another. It's a very nice technique. I also like to remove permissions from the underlying objects where possible. Then, every time I get to modify one of the client apps, I fix 'em, and try removing more permissions & such.

The only problem with such an incremental approach is that you often don't finish. (I've got one in a rather odd state right now.) Then if you have to turn over the project to someone else, they may be confused by it. Hopefully, they have a well-developed sense of "taste" and will continue the migration towards a rational end.

On my last project, I was the fourth person to work on it. You could plainly see that each one had their own philosophy. I didn't want a fifth philosophy in the code, so I just adopted the one that the majority of the code used. As for the database, it was just a bunch of tables. No relationships at all! Needless to say, I started tying things together in there. Another release or two, and at least the database will be in good shape. (Heaven help the code, though....)

--roboticus