Clustering responses to define dependent variable for logistic regression

Some colleagues of mine are working with survey responses, and are attempting to predict behaviors with demographic data. So, the plan is to define a dependent variable from some combination of responses to the survey questions, and then use a regression technique to model this dependent variable using other characteristics of the respondents. We all agree on the 5 or so questions that will define the dependent variable, but we disagree on how to specify the definition. I want to look at the actual questions being answered, and create a "score" as a weighted count of the'yeses' to the questions (weights based on how "on point" each question is to the behavior we are trying to define). My colleagues thought that this was too imprecise, and particularly criticised the'intuitive' weight assignment.