There's no way to cheat items with mods ("champion", "lordly", etc.) right now. It's possible to make a cheat script for it but that's a lot of work and most people aren't willing to put that in (because you'll have to make the script work for all items you want to get mods for), and if it's just for one item then it would be easier to just cheat with money and teleporting around the map until you find a store selling a champion horse.
Horse's death seems random. I once got my horse killed on its first ride. I reloaded my game right after because it felt bad. <_< It's either it gets crippled (leaving it Lame for a while), dies or just gets knocked out in combat.