I'd like a variant where there is both person accuracy p[i] and problem easiness E[j], and the odds of person i getting the correct answer initially on problem j are p[i] E[j] : (1-p[i])(1-E[j])

Ideally the updating procedure for this variant wouldn't treat everyone's opinions as independent, but it would also be interesting to see what happens when it mistakenly does treat them as independent.