We all know that trees and tall buildings obscure the view of what's behind them. This can have dire consequences as players may completely pass by something they may need but can not see because of their obscured view. So, just make important objects the player might want to collect or attack and/or avoid show up in their yellow-highlight all of the time instead of only when the player is behind the obscuring object.
As for the ability of player characters to hide behind objects and wait in ambush, just use the scents system of detection where stealth*intelligence is checked against perception*exploration.
Secondly are tall buildings and other objects that end up blocking the view of the terrain, namely wether or not the tiles behind the building are paved or not. Like in the late 90's game Dungeon Keeper where dungeon walls could be 'lowered' in height to aid the player in seeing what was going on via an option, this too could be applied to H&H and let village planners see behind their structures and notice if something has been altered; like if someone planted grass on a road behind a tall building to slow carts down as a form of griefing.