Dr. Taber,
Your idea `for a complementary variety of studies on the second (in
depth studies of individual learners, supported by large-scale
surveys to test out the generalisability of findings from
more `invasive'/interactive studies)' sounds like long due.

Let me suggest some topics and material to focus on.
How about
1. extracting the logic and worldviews used by great thinkers in
their conceptual works;
2. extracting the same (logic patterns and basic assumptions) used
while solving regular mechanical problems every civil engineer
should be able to do;
3. the methods and axioms we (those who will undertake the proposed
quest) have to utilize while performing the first two steps.

As the material why not take some major works by Plato/Aristotle,
Kant/Marx, Husserl/Wittgenstein for the first one;
Some major mechanical problems for the second one,
And our own cogitation for the last one.

The material is easily accessible, and we can do it on-line.
Do you want to try?

Michael (aka Mikhail) Chumakin, metodolog