Add a notion of IMPORTANCE to differences.

IMPORTANCE = 1 is indicated by differing definitions, and that's of 'most' importance.
IMPORTANCE = 2 is indicated by an object being missing in one database, and that's a bit less critical.
IMPORTANCE = 3+ is indicated by an object being missing, and being a 'child' of an object with a lower
                IMPORTANCE value.  Thus, if a table is missing, then columns and such will get IMPORTANCE
                incremented because they're less crucial than the missing table.

It USUALLY suffices to check for ... WHERE importance in (1,2)
Add foreign key association table for object types, renaming object types
Putting 'importance' in everywhere to provide priority information