Pacquiao would have an excellent chance, actually (assuming we get the Pacquiao that fought Cotto against the Benitez that fought the older Curry)
Benitez at his best is too big, too strong, and too skillful for Pac. Manny would look tiny standing next to him, and Benitez defense and counter punching would be too much for Manny. Pac would have next to no chance of beating a prime Benitez.
Bad matchup for Pac at 147 and 154. Benitez would be a nightmare for him. I haven't seen enough Benitez at 140 to pick that one.
Aye. Although I've always thought he loses this one particular match-up, you're right in that he has become useless in higher-weight MM's now for some reason.