He can use Off-Campus permit to work full time if he doesn't take any courses. But if he takes any course (even 1 course), the 20 hours restriction applies.
Other option can be work on this position part time if CTV can offer this option. Otherwise, he has to wait to start his work after this term. Usually, companies have the option for their new employee for the starting date.
Third option, drop all courses and work full time with Off-Campus Work permit. The academic will be delayed, but this helps to gain experience in his reference.