I wonder how many of the crew would have been redundant if that GPS nav system had been in the panel from day one? 
Possibly only one ... the navigator !!!, however, even when GPS was in its infancy, and laser gyro's were the "norm" for accurate measurement, the navigator role was still being pushed as a requirement due to the belief that the "enemy" would be able to either turn off/destroy/influence their effectiveness, so a man with a map and stopwatch to do "DR" was essential.
A secondary reason was the requirement for a minimum 3 man cockpit, pilot, copilot and one other .. the idea being that one man might go "rogue", he "might" influence another, but 3 people would be "safe" an all three would have to work together to arm and release the nuke.
The actual crew was 5 ... pilot, copilot up where that picture shows, and "down below" in a seperate compartment, the Nav Plotter, Nav Radar and Electronics Officer - the latter two were responsible for getting through enemy defences.