That's a really great suggestion thanks! I'm wondering how much a permanent reduce person would cost, it would be nice to be small and ride on a medium mount in case the DM is mean about taking your horse into dungeons. Seems like it needs to be human to fit in all the required feats.
Or Stronghearted Halfing, which gives an extra feat and it is also small so it can ride a Dire Bat.
As for later on, pick up some Riding Boots (DMGII, 12k) for another multiplier and if your DM allows you to rip the special double change while charging trait out of Knight's Sword (A&E) you can snag yet another (x7 damage!). Your weapon will be something like a +2 Gloryborn Berserker Valorous Wrathful Healing Collision Katori Resin Lance of Fearun which gives a lot of stuff. Like Spirited Charge allowing you to retrain all three mount related feats out for something else, it upgrades your Barb's Rage to Greater Rage, you heal half the damage you deal, and umm it's a +4 lance that deals 1d10+10+(everything else) damage with an x4 critical multiplier while raging/charging I think.
I had a recent deathball like Barb in some thread, dealt over 6k per charge in a 20ft area of death. And I didn't even use the TO Ubercharger's method of trying to apply mounted related effects with jumping effects. Sadly, I could do better (for instance it only used an x5 mod), charging is so broken. >.>
Minor thing: can't rage if Lawful and Paladins are Lawful. Still, great damage, which got me thinking: in a real game, and it seems to me that is supposed to be a played character, is all that damage necessary to 1-shot the enemies?
Even though you specifically asked for a charging build, I'll sugest you something somewhat different. Only one flaw.
Human Whirling Frenzy Wolf Totem Spirit Lion Totem Barbarian 2 / Fighter 4
Feats: Exotic Weapon Proficiency (spiked chain), Jotunbrud, Battle Jump, Improved Trip(Wolf Totem), Power Attack, Combat Reflexes, Improved Bullrush, Leap Attack, Shock Trooper.
+1 Valorous Spiked Chain.
A charging build which can also do BFC.