Ok, I think I've mostly cracked it... mostly. I followed your guide and created a new eastern based culture instead of barbarian. I then when through each step changing this new culture to egyptian and copied the egyptian UI from RTW 1.3 over the newly created eastern based culture UI files. Then in descr_settlement_plan.txt as well as the section around line 8576 you mentioned I editted the two sections above that (plans and plans by level) using text from RTW 1.3 settlement files to ad the egyptian paragraphs. This basically resulted in my new culture using mostly egyptian ITEM files in battle mode. I think the remaining buildings are the remnants of the Lombardii tech tree where it can't find egyptian equivalents... I've not tested heavily yet but I think it's close. Hopefully with a new tech tree we will have another set of ITEM files to edit unique to the new culture.