I think desert horses are great for HA builds, "only" require 6 riding. If you want to go a 4 riding build the Steppe Horse is good as well (just don't stray too far from your infantry teammates).
I think Crumb has a good build he's suggesting, you'd have 184 WPF in archery. I'm not sure about strength requirements of bows, think as long as you have the PD needed for them, you can equip them.