First Preference: Kid Gohan(if possible, in Saiyan and Namek saga garbs)
I chose this character because Dragonball Z is in a way about the story of Gohan and his steps toward being Goku's successor(well, that is until Goku stole the show again during Buu Saga lol), and so Gohan's kid appearance would mark a good spot for a smaller-scale figuart. They could even do a two pack of him, one with his Piccolo-esque garb from the Saiyan saga, and the other in the Saiyan battle armor from the Frieza saga, that way we could get his wild hair and his bowlcut!
Second Preference: Kid Goku
Yes, this is a weird choice given the releases so far, but it'd be the perfect way to get a Dragonball figure line going, plus he's really cool as a stand alone! Even displayed with his older self and the Super Saiyan forms it'd make a cool thematic display for the history of Goku. I watched DBZ before DB but I still believe the character's personality comes directly from Dragonball, and Kid Goku makes for great crossovers, as he isn't as OP as his Z counterpart.