I personally would look for a more modern stallion for your mare with more blood if you are looking for something that will jump closer to the base. The reason most horses take off far away from the base of the fence is because they lack the quickness in front to clear the front rail.
If I have the correct mare (Escada), then her blood content is less than Arko III at 31.25%. The potential cross would create a foal with 30.27% blood.
Is your mare quick off the ground? I rode quite a few Arko III offspring when I was riding in Europe a few years ago and granted, I knew nothing about the mares, but they all took a lot after their grand sire Argentinus both in their conformation and jumping styles, plenty of power, scope and rideability, but not much blood, a bit slow off the ground and not much refinement in type.
Here is one of the Arko III 8 Year Old Stallion that I was able to work with.
Just my thoughts 