Large characters like half giants and ogres, could/should potentially be allowed to have the spirited charge bonuses from being mounted, apply while on foot, as if they were mounted - the reason there is no mount for them is because of model issues if I recall, but if we give them the spirited charge effects while on foot, they don't actually get mounted combat boosts (meaning no AB/AC boost from being mounted - because they aren't) and still have -1 AB/AC from being large, and have to pay the Mounted Combat feat tax, so it seems like a pretty hefty tradeoff to allow them some build variety and actually have cavalier be a possible class for them.
Thematically, a half giant running into someone and messing them up also just makes sense. You don't need a horse, you're 10-14 feet tall.
<3 ty