Ugh, I'm not too strong on the to-hit department, to be honest... I'd say your best bet would be an item of wraithstrike/true strike, maybe even both.
I'm also pretty sure charging will be our main asset here. Feat intensive, but that can be worked with a couple of fighter/feat rogue levels. With flaws, that can easily go into fully-fledged dragoon by level 6 to 9, and if you can get turned into a centaur, that'd help. A lot, actually. Even better if it's a flying centaur.
Still, let's say level 9 you'd have 22 str before buffing, with 8 BAB(two levels of feat rogue, maybe two of psywar for the feats, not sure if that'd be okay?) shock trooper, leap attack and all, that would be +41 damage on average per hit. With a 1d8 weapon, averaging 45.5. We need either a 7x multiplier to crit damage for that to work, or to raise your str/dmg too. By raising our average damage by 6 we'd need just a 6x multiplier, so I believe that's the easier path. Adding a second hit could work, maybe. Pounce sould do the trick.
Well, that's gotta be challenging, but I'm sure it's possible. Just not really for a newcomer in op-fu as me.