His current leadership is really low considering his role in books and film The KingElessar should have much greater impact on Gondor even if Lvling up to 10 difficulty is increased.
1)Why not remove Denethors when Aragon reaches lvlil 10 and he can enter the Citadel like Saruman and use improved or increased versions of Denethors abilities like banner carrier to a Numenorean captain or Denethors massive attack bonus in short area to him
After all the mod depicts Aragon wearing crown at lvl 10 and Denethors dead by then lore wise so shouldn't it be like that
2)Or at least a general increase in lvl 10 Aragon leadership for the man who led the last great battle before the gates. Maybe an movie wise Active ability like Theodens glorious charge here : For Frodo or Hour of Wolves dialogue part from the film