How do you Optimize a schedule excluded resource and cost and Analyze risks and establish time contingency w/o knowing the impact of Pn date on cost

In my opinion a schedule not loaded with resources and costs is just good for preliminary phase and has to be developed with allocating resources and assigning costs to tasks so that the best target plan be selected among different scenarios based on optimization. Then identified risks has to be analyzed and the Pn date should be evaluated based on both the time and cost contingency. The best alternative then would be the baseline which would most likely comply with reality that could happen on the ground.