Two excellent choices. Due to Season 2 being half off on PSN, I just got back in, so what great timing!
I don't even like GT and I agree that Baby should be in the game in some form, one of the few elements I liked from that series. As for any others, honestly there's not many left I can think of I would care about. Roshi should be in it eventually. Whis too. I sorta like Pikkon but I wish his hat wasn't Marge Simpson head-shaped and he looks bad without it too. I won't be mad if Dabura is added but he never appealed to me. Pan would be fine, I don't hate the character rather just how the writers made her get into trouble constantly so Goku could fix everything (the GT writers themselves admitted to sticking to this formula during the entire first arc). There's probably others I'd like but just forgot about.