A pilot is indeed capable of multiple actions. Page 169 says “Each additional action after the first one gives a -2 to all actions”.Add up the number of actions excluding the first one, and apply a -2 for each remaining action to ALL actions that round. If you are doing Advance, Evade and Ram, for instance, you would take a -2 penalty for Evade and Ram making it -4 total, and apply that penalty to all actions that round, including Advance. Dividing your attention in a stressful situation can lessen your overall ability!
If your crew is normally 5, and for some reason one is unable to perform, the pilot and captains roles become merged. The “captain” part rolls for initiative only, and since he’s busy piloting, is unable to issue any commands to the crew. Since he’s only rolling initiative (a free action) and nothing else, the “pilot” part wouldn’t get a -2 right at the start.
Each crew member can only be in one position at a time, think of each person at their own specialized computer or desk. In a combat round, you wouldn’t be able to pilot the ship then run across the bridge to the weapons station and fire a few rounds then run back to the pilot’s station, just not enough time. If a person doesn’t want or have any actions to take, they would stay at their station because the next round isn’t that far away and could be needed. It is entirely possible though, to have a crew of 6 or 7 or more, with the extra people running extra stations, 2 different gunnery stations for instance, or 1 sensor operator locking targets and 1 breaking locks. This would require more players or some other means of handling a larger crew.
As far as changing positions, I would think it could be possible but only at the start of a round, perhaps with a penalty to show time spent reorganizing?