I implemented further tweaks with v2.2. I included more territory to the East so as to ensure Astrakhan abutts Persia. This allows Russia to gain further leverage on Persia (the new Caspian Sea also provides for yet another way of getting Russian units into action down there).
Persia strikes me as the minor power most likely to be conquered last. After all, neither Russia or Turkey will want the other to conquer it and will be mindful of keeping the neutral in being unless of course they can conquer it themselves and thus gain a leg up on their rival.
Really, I think either power can only gain it if the other is distracted, weakened or plain incompetent as otherwise that player will want to prop up the Shah rather than seeing that critical position being lost to a then very dangerous enemy. One's backdoor would then be wide open! Not a pleasant prospect.
Well, just a short progress report...