Yes, I see what you're getting at. And I suppose I agree in principle.
This issue however applies system wide. Every package we've ever used has needed work on its 'core' files to suit our purposes. I suspect thats pretty true of most people (?).
Therefore what you suggest is actually applicable all over the place.
The problem I can see is one of compromise. To instigate this level of 'customisation' in each package would surely represent a compromise in terms of performance/maintenance/development. Also, given that in any site, the 'users' are likely to be one of the most commonly referenced elements, that compounds the difficulty in this case. (unless someone has a whiz bang clever way to do it).
Perhaps an alternative (and I'm by know means backing it) would be to consider what 'core' files in packages actually consist of.
My thinking is that at present, each package offers (or trys to) too much in terms of interface and page flow. I'd rather see packages offering more minimal interfaces, but organised as easily re-usable fragments. Offering therefore more scope to organise the package as yuo require....
