Well lets pretned we take this idea seriuosly shall we?
Lets get some stats down first
hit points 200
body armor 100
requirement 8
horse speed 20
horse maneuver 18
horse charge 55
Price about 200,000 gold
Well sure but you're only gonna be able to use ranged from it.
So it'd get abused by my mounted xbow character a lot
Also, we can't add horse trample (I think) so you'd have a head on collision with no damage to the horse. You'd be out paced by everything, including some infantry. You'd fall 20ft when the thing died and take no damage.
Everyone would aim for you because you're so freaking big
So no
But I'm all for camels, they'd be nice