1. See the Siddur Eretz Yisrael and Rav Lior’s introduction therein. Many of the nusha’oth are fluid, and there is no hard and fast rule. For instance, the final blessing “Who blesses His people Israel with peace,” is always replaced with “Who makes peace.”
2. If we assume some rule, then often it is the idea that the text of the prayer reflects biblical idiom.
3. Moreover, some blessings don’t need mention of Israel. How would it be worked into, e.g., “Bonei yerushalyim,” and “Melech oheiv tzedaka umishpat,” or “M’vareich hashanim?”
Keep up the good work.