Given how many marriages end in divorce (some claim that as many as half of children see parental divorce), the very least colleges can do is clearly state how they handle divorced parent situations, and how to use their net price calculators in those situations. Princeton does a good job here (but note that how it handles some parent situations may not be the same as how other colleges handle them): https://swebapps.princeton.edu/FinAid/finaid_form.pl
Regarding the more unusual types of income that can be problematic with NPCs and FA calculations, a college can at least state on its web page that leads to the NPC appropriate disclosures about accuracy or lack thereof when such income exists, if it does not want to implement an NPC that handles those types of income in a way that gives an accurate estimate of its actual FA.