Dependent options within dependent filters?

This module is almost a perfect solution to my current project (thinktank.arizona.edu), but there was a place where it fell short. I am thinking that others may want the same functionality I was trying to get, so I'm describing it here in a feature request.

What I was trying to do was this:
Make dependent filters show, but also restrict which options the dependent filter has available. For instance, say I'm trying to run tutoring services for students and there are a variety of ways they can be tutored (e.g. exam preparation, 30-minute appointment, drop-in tutoring, online tutoring, etc.), but we only provide certain types of tutoring for certain subjects. What I would like to do is guide the user through a set of filters; first select the subject, then select one of the only available tutoring service types for the subject.

For example: a student selects "Math" for the subject and then the tutoring service type filter shows up with the options "Drop-in Tutoring" and "Exam Preparation" and "Online Tutoring", or a student selects "Writing" as the subject and then a tutoring service type filter shows up with the options "30-minute Appointment" and "Drop-in Tutoring."

I tried doing this with multiple service type filters restricted to different options then made them dependent on different subjects, and it almost worked... except some results were left out or no results were shown at all. I've attached a feature of my sandbox site with the view I attempted and the tutoring service content type. I think it would be very useful to have variations of one type of filter dependent on previous selections—just a thought.