About Who's Who's DF, wouldn't a raptor be most fitting for him? They were very fast and they could actually use their arms. I think it makes the most sense for a swordsman.
Sasaki to me looks like a stegosaurus or ankylosaurus user. He's the "buffest" of the group and doesn't come across as someone who uses much speed but leans more into strong durability and endurance. If Oda is just using the popular dinosaurs, I expect one of those two to be here. Most people know about them and tbh, only Sasaki looks like he'd fit.
Edit: just realized that there are a lot of different types of raptors. Velociraptor for Who's Who to specify. It follows the logic of what I said as well as the popular route.