This is a very unconventional character I will admit off the bat. My group is playing in an "everything, including the kitchen sink" sort of campaign, with the main rules being basically Pathfinder, so pretty much any book would be allowed. My characters current build is an alignment agnostic paladin variant (I'm NG and probably gonna stay that way) based around the Pathfinder pally for 4 levels, and 2 levels of Pathfinder barbarian. Planning to pick up a level in Crusader and then 7 in RKV, and then, assuming the DM agrees to tweak it a little to be better balanced something like the Dreadnought from d20 Future for a few levels, the DM would be likely to ignore any levels in the class that give "Bonus Feat" which would reduce it to 3-5 levels.
The main focus of the build is progressing towards a lock-down sort of theme, forcing people to stand and fight me, taking AoOs whether they do or don't, and using DR to mitigate the damage from all the hits. I'm mostly looking for a PrC to fill up the last 3 or so levels of the build that would give me some casting advancement as a Paladin to flesh that out a little (already picked up Battle Blessing to make it that much more useful) and help me bring the pain. I'm permanently Large and increase to Huge when I rage in case that's helpful.
tl;dr Feel free to mock me for being in a crazy/broken campaign. Any sources. Looking for a PrC to give three levels of paladin casting in 3 levels and hopefully enhance my tankiness. Thanks in advance for the help.