One of our members, November, created a neat little tool to do the kind of combination you are considering. It is the Mixed Mass Percentage Calculator tool shown on the right hand side at http://foodsim.unclesalmon.com/.
Just use the pull down menus to select the two flours you wish to combine (all-purpose flour and KASL), and enter the mass (weight) of the target flour (bread flour) and its protein content in the specified blocks, and you will get the amounts (weights) of the two flours to combine. I checked the focaccia dough recipe at page 136 of Peter Reinhart's book, and the amount of flour called for is 26 ounces. I would use that number as the target mass in the tool, and I would use 12.7% for the protein content of the target bread flour. The combination of flours may not perform identically to bread flour, but it may get you close enough for your purposes.