The only issues I see with milling the splines is, the hub now rubbing on the splines on the axles. Going from memory, the axle is pulled into the with a nut, as the hub and splines have a taper. It would be great to be able to machine, and add some sort of bearing, to tighten the axle so it stays centered in the hub, but free wheel, with the bearing. Also if someone could adapt or come up with a set of locking hubs, would be the idea way to go. As my front axle has some pitting in the ring and pinion, and the less wear the better for me , just my opinion on the topic