Unoccupied workstation

That's a good question. Because this is a "design" based rating system I could see the reviewer saying that the space is "designed" for 10 people and therefore even the unoccupied desks need to be included in your total. Plus, who's to say that those desks won't be used by visitors who would want to have individually-controlled lighting. If you are only including 6 task lights in your LEED submittal then I'd HIGHLY recommend that you explain profusely how you will furnish task lights as the other desks get occupied. For example " the office manager is given a purchase order for another lamp whenever a new employee is hired, etc.." I think you already know this but just in case: only 90% of individual occupant areas need to have task lighting.

Yes, because you have a designed space for 10 desks, I would include controls for those desks. Eventually - your intent, presumably - is to have all desks filled and in this case you'll want to ensure that all desks have suitable controls.