[henshinzero]

If there was a dinosaur rider there are two I'd go for.
- One with the power of all dinosaurs
&
- One with the power of prehistoric beasts

Perhaps sports can be involved too somehow. The dinosaur rider would be a caveman frozen for centuries until thawed out learning about the modern world. But is willing to protect what's pure and true.

He can play sports and fight in gladiatorial battles.

The key item is a problem.

As for a ninja rider...

The key item I go for would be beyblades.

And the monster rider since Kiva...?

They need to do it again! Start something fresh!