Today, it is obvious that Lucas made a wise decision. One reason is Ford’s abrasive, sarcastic delivery, which sounds perfect for a hardened space adventurer.
Han Solo’s derisive remarks to Princess Leia and Luke Skywalker would have been less effective if they hadn’t been spoken in Ford’s gravelly, attitude-laden voice, and a human face certainly helped with his exasperated looks. A flattened, green face just couldn’t have done it so well.
Having Ford in the film also allowed more sex appeal. The role of the hot female was easily filled by Leia, who became an instant sex symbol of the early 1980’s. However, if Solo had been a green alien, he could not have been the film’s leading man. (Even in these enlightened times, interplanetary sex is still frowned on.)
The film would have been left with only Luke as the starring human male, and with all due respect to the young Mr. Hamill, he was not exactly a he-man.