It depends on what the rules are for your exercise.
In general, the answer would be No. A full scale disaster exercise is just that. You are testing an already published deliberate plan with assigned roles and resources and the time for debate and discussion has long since ended. Your only purpose is to demonstrate your knowledge of the plan and then engage and get the job done and be evaluated. Afterwards, you can critique improvements in an after-action report or hot wash-up session, then revise the plan accordingly. The general rule is, you test first, fix later. You don't try to fix while you're still testing (or exercising).
