Due by, due on, due for - what's the difference?

I think two of these are more-or-less interchangeable, but one is not. They also lend themselves to different levels of clarification and specificity in their request, and a different order to the information presented.

"Due by" implies that there is a set time of when it is due. "The sales report is due by 12pm on Friday." The day something is due follows the time, which is given more importance. The time can be stripped and the sentence will still work, one just loses the precision of the request.

"Due on" places more importance on the day something is due, and not so much the time. "Your membership fee is due on Friday." A specific time can be added but it would follow the day/date.

"Due for," however, is more about the person or event something is due for, and not so much when it is due. "Is that essay due for Mr. Green's class today?"

I see no substantive difference between these three. Even with "due by," I think it would be ambiguous as to whether someone wanted x by the beginning or the end of Friday. Personally, I would use "due by" to cover all three and would take it to mean something like "up to and including Friday." "Due on" Friday seems strange because it could imply that it is due only on that day and couldn't be handed in sooner, and "due for" sounds idiomatically strange, with "for" seeming like a wrong prepositional choice to me.