Just off the top of my head, make Krillin, Yamcha, Tien, Piccolo, Yajirobe and even Chiatzu stonger, not on the same level as the saiyans, just enough to make useful. in Dragonball they were all at one time on the same level as Goku, making them essential... although, they never all got together to combat a mutual enemy like in DBZ. the sad thing about DBZ is that Yamcha ,Chiatzu and Yajirobe pretty much ran their course by the end of the Saiyan Saga. Though considerably weaker than the others, Tien was essential and helpful to the main warriors till the end, though he was hardly around as well. Krillin was done for after Frieza Saga and Piccolo faded away too after his second encounter with Cell.