Monstrous Warhorse

I came across the images above on Tumblr(here), and thought they'd make for some very interesting variants to normal mounts, or even just some potentially surprising creatures for a fight. Regarding stats, they'd be slightly different between the quadrupedal and bipedal forms. Both would take the base stats of the Warhorse found in the PHB. Given the nature of their mouths as depicted, each form also has a Bite attack(+5 to hit, 1d6+4 Piercing damage).

The quad form would also take the Trampling Charge trait, where if the horse charges at least 20 ft at a target, the target must make a DC 14 Strength save to remain standing, and if it fails, the horse can use a Bonus Action to make an attack with its hooves. The only difference here would come if the horse's front legs were claws instead of hooves, in which case the attack would be Slashing instead of Bludgeoning.

The bipedal form, while still able to be ridden, would lose the Trampling Charge trait and instead gain a Grappling attack. Creatures caught in its claws must make a DC 14 Strength save to escape, and if they fail, the horse can take a Bonus Action to make a Bite attack(with Advantage from the grapple).

I'm seriously considering putting these into my own campaign shortly, but since I'm still new to the whole creature/stat creation thing(heck, even new to the whole DM thing still), I look forward to any and all feedback this garners.
{Edit} I also haven't thought of any special name for it, so any ideas on that front would also be appreciated.