With respect to the issue of handling cast/crew for box sets, assuming it goes forward (see discussion on TV Series Contributions):

For a given profile, if it contains references to other profiles (ie: it's a box set), then in the cast lists, list cast in order of: current profile, [divider: disc 1 name] disc 1 cast list, [divider: disc 2 name] disc 2 cast list, etc.

You might restrict it such that it only lists the additional casts if the profile ID that it's considering pulling a cast list from uses a disc ID that's included in the current profile's list of disc IDs, or if the profiles have been added by disc ID rather than UPCs (optional variants).

Crew lists might be a bit trickier to arrange, but still basically the same thing.

The main issue would be duplication if you have the complete cast list on both the parent and children, but if only the children have cast lists, those who only want to deal with the parent still get all their info in one place, just need to keep the children hidden on your DVD list.