Since we're stretching into the realm of fuzzy TO
Wizard 5*/Paladin 2/Knight of the Blue Moon 1**/Beastmaster 2/Halfling Outrider 10
*high one warrior wizard AND spontaneous divination ACFs (required for KotBM)
**City of Splendors: Waterdeep - grants a mount and lets you stack wizard levels if you don't have a familiar
feats: racial emulation, natural bond, whatever else is needed for prereqs
I don't think this works with the cohort/mount idea, but whatever.
You have a mighty morphing mount 18/animal 18/familiar 5, which gives you: +20 HD, +15 NA, +10 Str, +6 Dex, Int 9