You would hate me ... But still I have to say that there is one problem - in some areas plunder would be very big - in fact many wars were pure plunder which RTW is not depicting.
Making staying on enemy land very expensive won't be historical - in fact (exept some regions - forests, deserts) staying on enemy teritory should in fact give you money, not take it from you. On the other hand, in your land army needs to be fed and paid by your own men ...

also is there any posibility to give money to army winning a battle if anemy is destoyed or routs? It should be scaled to enemy army size, as it is to reflect capture enemy camp, loot the dead, sell captives.