Missing depends seem to occur from insufficient testing of all combinations on flavors.
If each package had an absolute depends list starting from a hypothetical nothing (or at least from the smallest micro slitaz), it should be easy to generate a relative depends list by dynamically crossing out packages already on any selected flavor iso or custom installation.
I think tazpkg already does something like this but starting from a flawed relative depends list based on human error.
The website's packages page could require selection of a specific flavor iso to dynamically generate an accurate relative depends list by comparing two knowns according to the latest, updated information.