Kuririn is human, don´t discriminate against nose-less people, most anime girls these days don´t have them lol.

Kuririn was stronger than Videl even when he was, was, 12 years old as a pupil of Mutenroshi´s. Remember the 2nd tournament when he and Goku fought each other? Video never was on that level. And Kururin, too, learned flying by himself.

Again, I´m not saying it´s easy to explain a reasonable powerupgrade for humans. But ... I feel it would be possible.

Worse case: All the weak non-saiyan characters (which even C17 counts for) get to partake in the upcoming tournament and can keep up with NO explanation given at all. Now that would suck :/