Saiyans are just humans with tails. The real problem is that they all look and feel too similar, and that half of them are Goku.
But me, personally, I'd buy FighterZ in a heartbeat if they added all of the Tenkaichi Budokai participants (Nam, Chappa, Giran, Ranfan, etc.), the Red Ribbon Army bosses (incl. Murasaki, General Tao, Eighter/Suno, etc.), the pirate robot, the bear bandit, some Namekians (incl. Piccolo Sr./spawn, Kami/Popo, Nail/Dende), Yajirobe/Korin (remember he's really a beast), etc.
Pilaf, Shu, and Young Mai can be supports for Future Mai. Launch, Bulma, Oolang, and Puar can be a unit. Roshi and Turtle can be a unit. Crane Hermit and Chiaotzu can be a unit.
The possibilities are endless, and the OG Dragon Ball characters would add TONS of variety to the metagame, as well as in terms of general aesthetics.
Then we've got Babidi's minions, Frieza's unused minions, and so on.
It doesn't have to get Xenoverse big, but they should at least focus on martial artists for the most entertaining gameplay possibilities.