Magnificent idea, for example doing the thieves guild quests in Riften raising the income into the city if you chose the imperials and had Maven as Jarl... It would not make any sense at all for only solitude and windhelm to have a higher sallary, being that windhelm is a pretty poor city and that whiterun is skyrims trade center, on top of that you dawnstar windhelm and solitude all fighting for the best "tarriffs" and so multiple cities would have different depending on the personal position, and solitudes price would go down because of the multiple thanes it already has, and the payment to more guards then any other city, there are almost to many factors to factor into making this mod a reality in a way that would satify most