Johnstone's theory of improvisation (and acting in general) is that most of the weight of convincing the audience is carried by relative status distinctions among the actors.
By my recollection (I don't have the book in front of me) the status distinctions that he writes about are not among the actors, but among the characters that the actors are portraying (as you say in your review). I doubt if a theatrical company could long survive if the actors themselves were ceaselessly jockeying for position in the way Johnstone has the fictional characters doing. I am unconvinced of the usefulness of taking this as a key to human relationships in the real world. What Johnstone did was to take a single aspect of human relationships and use it as a cantus firmus on which to construct theatrical scenes. It convinces the audience not by resembling life, but by resembling a single idea about life, much as a cartoonist makes an instantly recognisable face with a few lines by concentrating on a single, simplified physical feature.
You could take any ubiquitous feature of real life and use it in this way as a key to theatrical composition. If Impro had been written in the 60s, the key that it presented might have been sex: everything the characters did would be constructed on the basis of being a negotiation, overt or covert, about whether, when, and with whom to have sex. Social class can serve as a key, from which one gets "stock characters" and comedies of manners. Pinter found a minimalist key: explain nothing and insert unnaturally long pauses between conversational turns. The audience fill the gap themselves by confabulating the characters' thoughts, and wonder how Pinter made his dialogue sound so realistic. At least, they did at first, but this happens with all new theatrical techniques. They begin by being lauded as refreshingly realistic, but with time they are seen to be no less artificial than their predecessors.
Recent brainstorming sessions at SIAI (with participants including Anna, Carl, Jasen, Divia, Will, Amy Willey, and Andrew Critch) have started to produce lists of rationality skills that we could potentially try to teach (at Rationality Boot Camp, at Less Wrong meetups, or similar venues). We've also been trying to break those skills down to the 5-second level (step 2) and come up with ideas for exercises that might teach them (step 3) although we haven't actually composed those exercises yet (step 4, where the actual work takes place).
The bulk of this post will mainly go into the comments, which I'll try to keep to the following format: A top-level comment is a major or minor skill to teach; upvote this comment if you think this skill should get priority in teaching. Sub-level comments describe 5-second subskills that go into this skill, and then third-level comments are ideas for exercises which could potentially train that 5-second skill. If anyone actually went to the work of composing a specific exercise people could run through, that would go to the fourth-level of commenting, I guess. For some major practicable arts with a known standard learning format like "Improv" or "Acting", I'll put the exercise at the top and guesses at which skills it might teach below. (And any plain old replies can go at any level.)
I probably won't be able to get to all of what we brainstormed today, so here's a PNG of the Freemind map that I generated during our session.