All-cav Empire lists are really hit or miss... If you want to do it, more power to you. You ABSOLUTELY need a couple of mounted Warrior Priests in
a list like this though. The re-rolls to hit/wound are invaluable when running with calvalry.
Also, maybe break that big block down into two more managable blocks? 24 makes one hell of a big, attractive target.
Finally, I'm curious as to how you're going to deploy the War Altar? I get the general concept (I think)... The big block ties down the enemies
large bodies of infantry, while the Gryph's are there to rip up flanks... But are you willing to take the War Altar along for the ride?