No way Leonard would have schooled Pacquiao. Pacquiao's south paw stance and punch combination speed is more than anyone Leonard ever faced. Although at a much higher weight and older Leonard, Hagler walked though Leonard's punches. Pacquiao would have been able to land at least 20% more punches than Hagler did.
Very interesting note however about Leonard, did you know that he fought 25 times in less than a 3 year span from start of his career 77-79 until he fought his first 15 rounder with Benitez. He made an equivalent of $4 (1.5) Million in today's money for that fight. He fought Duran twice after that and made an equivalent of $23 (9) million for the first and $20 (7) Million for the second fight. He had 5 more fights and his first retirement in 1982 just 5 years of fighting after turning pro because of a detached retina.
Bookmarks