Javalry and other throwing cavalry need to resign to the fact that they need to rely on riding speed bonus and their higher strength to do damage. In other words, that 5 PS is a waste. For cav, riding replaces athletics, so at this point you are still pure as long as you don't waste points on athletics. You can throw stuff with points in PT and WM, ride and HA. And that is it. Horse ranged need to be wise about spending their points, unlike ground pounders who have more leeway. The only horse ranged that can afford to have spare points is a HC, since he can ignore a power skill, max out WM and HA and riding, and still have 2 points left over. Other horse ranged find it very difficult to hybridize, and don't have the points to spare.
In short, if you add melee or athletics to your horse ranged character, it becomes a hybrid, which are just not that good these days.