Unfortunately, I think we only have time to implement a fix to this specific problem at the moment.
However, when I first read the acs_objects datamodel one of the first things that struck me was the fact that object types ain't objects. So I find your comment regarding this very interesting and it confirms my gut feeling that flexibilty has been lost because of this decision.
I don't know what your personal schedule is like, but down the line this issue is something that clearly should be looked into. As time goes on I think we'll identify a considerable number of core design issues that are worth analyzing with an eye to improving the system. It would be great to have a small group of folks who have experience with the 4.x guts take on this task.
I'm definitely thinking in terms of the future, perhaps fall or early winter, as a time to consider reviewing the basic design of objects, permissions, and other core "stuff".
