I concur. There are precedents for 3 HD "playable races", such as the bugbear.
I'm also indifferent as to the horse from which we pull ability scores.
Ok, then, starting from the light warhorse, how about Str 16, Dex 13, Con 17, Int 14, Wis 11, Cha 14?
Advancement by character class, sure.
I could see a bonus on saves vs fear effects.
As for using weapons, I could see giving them non-proficiency with all weapons (including simple weapons) other than those Cleon suggested.
I'll agree about the weapon nonproficiency.