RTF is a global modification that replaces all towns in the game.

That's cool! Could you make it so that a Ranger can ride a Dark Knight's lizard, but the shooting animation is preserved? Something like a mounted archer from the Dungeon faction. I would really like to see that.

No, I can't do that. If you need to preserve the shooting animation, you'll have to apply all the animations as effects to the entire creature. Hypothetically, you could rename the HIP bone in the animations or in the Ranger's skeleton. Then, it would move normally, but in the air, as if suspended by its rear. Then, you could attach it to the rider's rear with an effect, and the animations would match up properly (I did this with riders on wolves, but there was originally a goblin with a HIP bone and the Ranger's animations had a HIP bone).
However, I don't know how to work with skeletons, so I can't do that.