Bardock might actually be too good a character - as in, he has a very tight character arc, and that's what defines him before anything else - to translate well into a fighting game character. Despite his awesome fights (well, fight) in the TV special, his shtick isn't fighting. It's going from a murderous mercenary to a tragic character who is powerless to save his race against an almighty tyrant and the incredulity of his own people. As someone pointed out, his techniques work in a narrative context, but they're not really techniques. It's just him fighting however he can with his instinct. He's not a martial artist type character, nor a typical shounen character. He's very different from every other DBZ character. Trunks has a bit of that quality to him thanks to the History of Trunks special that fleshed out his character and his background, but he's still a fighter with his own techniques and the traditional martial arts structure of being trained by a master who taught him everything he know.
Contrast Bardock with Goku and pretty much every other main and secondary character in the series: they all have character traits and, most importantly, distinct techniques and/or physical attributes. From the Kamehameha to the Taiyouken, from the Kikouhou to the Soukidan, from stretchable arms to the ability to bend and modify their bodies at will. Even those who don't have named techniques in the manga or anime still have recognizable attacks, like Frieza's "death beam". Some of them have character arcs, but it mostly boils down to "bad guy becomes good" or "arrogant dude became more humble", and in some cases, those arcs are all over the place (did anyone say Gohan?). But it doesn't matter in the context of a fighting game. All they need is to have enough techniques that can be made into special attacks, and to have had enough screentime/manga pages to be made into a regular moveset.
With all that said, I hope we get a story mode à la Budokai 1. That stuff was mindblowing at the time, and the best kind of fanservice, especially for people who wanted to get the DBZ experience in the original language. None of that alternate reality/time travel bullshit of games like Budokai 2 and Xenoverse. But I have a feeling I'll be disappointed. This really doesn't seem to be the focus, and I don't know that the 3v3 structure and "1 transformation per character" rule will lend themselves well to the retelling of the story. I mean, how can Piccolo and Goku against Raditz work when it's 2v1, Goku isn't a Super Saiyan, and Raditz might not even make it into the roster?
[FAKE EDIT] Note: when it comes to Bardock, I'm only talking about the original TV special where we first learn about him and the story of the demise of planet Vegeta. That shitty "Bardock is the legendary Super Saiyan who defeated Frieza's ancestor" doesn't exist.
