Adding something exterior to the current building footprint can add fan amenities, including concessions, bathrooms, and concourse space. That part is fairly easy to do. It just costs money.
Adding 2000 to 2500 seats is not feasible. That is a 25%-30% increase in capacity. If you replicate the student section in place of Sec 118, that is only 1500 seats. But if you are considering those premium seating, you would want actual seats, not bleachers, so you could only fit about 1200 seats. That would also mean eliminating the handicapped seating and glass office area over the concourse.
Adding seats to the open corners by the student section is limited. Although that space seems huge, because of the posts there is actually very little space where you can see the court. Go to that area next home game (or stand in the opposite corners on the concourse) and you will see what I mean.
The real seating need at the RAC is additional premium seating. So that probably means converting the glass offices to club space. Also, any reconfiguration of the arena would have to include improvements for TV broadcasts.
In reality, if Rutgers were to look to reconfigure seating in the RAC, you are looking at spending a lot of money, and the best options would only get you about 750 to 1000 additional seats.